Herbicidal isoxazolo[5,4-b]pyridines

ABSTRACT

The invention relates to isoxazolo[5,4-b]pyridine compounds of formula I, 
                         
to the agriculturally useful salts of isoxazolo[5,4-b]pyridine compounds of formula I, and to their use as herbicides.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 13/811,095, filed Jan. 18, 2013. U.S. application Ser. No. 13/811,095 is a National Stage application of International Application No. PCT/EP2011/062454, filed Jul. 20, 2011, which claims the benefit of U.S. Provisional Application No. 61/366,535, filed Jul. 22, 2010, the entire contents of which are hereby incorporated herein by reference. This application also claims priority under 35 U.S.C. §119 to European Patent Application No. 10170416.1, filed Jul. 22, 2010, the entire contents of which is hereby incorporated herein by reference.

The present invention relates to isoxazolo[5,4-b]pyridines of general formula I as defined below and to their use as herbicides. Moreover, the invention relates to compositions for crop protection and to a method for controlling unwanted vegetation.

Compounds having an isoxazolo[5,4-b]pyridine moiety are known in the art. US2009163545 describes such compounds as lifespan-altering for eukaryotic organisms. According to WO2009015208, particular urea derivatives show an antibacterial effect. Potential routes for synthesis of isoxazolo[5,4-b]pyridine compounds are known from Elbannany et al, Pharmazie (1988) 43(2), 128-129 and Volochnyuk et al, Journal of Combinatorial Chemistry (2010) 12(4), 510-517.

In agriculture, there is a constant demand to develop novel active ingredients, which complement or outperform present methods of treatment regarding activity, selectivity and environmental safety.

It is therefore an object of the present invention to provide chemical compounds, which are suitable as herbicides. In particular, it is an object to identify chemical compounds with high herbicidal activity, preferably at low application rates, while leaving desirable plants, e.g. crop plants, unharmed.

These and further objects are achieved by isoxazolo[5,4-b]pyridines of formula I as defined below and by their agriculturally useful salts.

Accordingly, the present invention provides isoxazolo[5,4-b]pyridines of formula I

-   -   where in formula I, the variables are as defined below:     -   R¹ hydrogen, halogen, hydroxyl, C₁-C₆-alkyl, C₁-C₆-haloalkyl,         C₁-C₆-alkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,         C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl,         C₁-C₆-alkoxy, C₁-C₆-haloalkoxy, phenyl, phenyl-C₁-C₄-alkyl;     -   R² hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,         C₁-C₆-alkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,         C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,         phenyl-C₁-C₄-alkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl, C₁-C₆-alkoxy,         C₁-C₆-haloalkoxy, C₁-C₆-alkylthio, amino, C₁-C₆-alkylamino,         N,N-di-(C₁-C₆)-alkylamino, heterocyclyl; wherein the         heterocyclyl moieties of R² can be unsubstituted or substituted         with one or more radicals selected from halogen, nitro,         C₁-C₄-alkyl, C₁-C₄-haloalkyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy,         C₁-C₄-alkoxycarbonyl, heterocyclyl, phenyl;         -   or R¹ and R² together form an C₃-C₅-alkanediyl;     -   R³ hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,         C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,         C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,         C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,         C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,         C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,         heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,         C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy,         C₁-C₆-haloalkoxy, C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino,         C₁-C₆-alkylamino, N,N-di-(C₁-C₆)-alkylamino, heterocyclyl,         phenyl; wherein the heterocyclyl and phenyl moieties of R³ can         be unsubstituted or substituted with one or more radicals         selected from halogen, hydroxy, nitro, cyano, C₁-C₄-alkyl,         C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,         C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy,         C₁-C₄-alkoxycarbonyl, C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl,         C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, heterocyclyl,         phenyl;     -   X OR⁴, SR⁵; NR⁶R⁷;     -   R⁴, R⁵ hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl,         C₁-C₆-hydroxyalkyl, C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,         C₁-C₆-alkoxy-C₁-C₆-alkoxy-C₁-C₆-alkyl,         C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₂-C₆-alkenyloxy-C₁-C₆-alkyl,         C₂-C₆-haloalkenyloxy-C₁-C₆-alkyl,         C₁-C₆-alkoxycarbonyl-C₁-C₆-alkyl, aminocarbonyl-C₁-C₆-alkyl,         C₁-C₆-alkyl-aminocarbonyl-C₁-C₆-alkyl,         N,N-di-(C₁-C₆-alkyl)-aminocarbonyl-C₁-C₆-alkyl,         [N—(C₃-C₆-cycloalkyl-C₁-C₆-alkyl),         N—(C₁-C₆-alkyl)]-aminocarbonyl-C₁-C₆-alkyl,         C₁-C₆-alkoxy-aminocarbonyl-C₁-C₆-alkyl, C₂-C₆-alkenyl,         C₂-C₆-haloalkenyl, C₂-C₆-alkynyl-C₂-C₆-alkenyl, C₂-C₆-alkynyl,         C₂-C₆-haloalkynyl, heterocyclyl, phenyl, heterocyclylcarbonyl,         phenylcarbonyl, heterocyclylcarbonyl-C₁-C₆-alkyl,         phenylcarbonyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl,         phenyl-C₁-C₆-alkyl; wherein the phenyl and heterocyclyl moieties         of R⁴ and R⁵ can be unsubstituted or substituted with one or         more radicals selected from halogen, C₁-C₄-alkyl,         C₁-C₄-haloalkyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy,         C₁-C₄-alkoxycarbonyl, heterocyclyl, phenyl;     -   R⁶, R⁷ hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₂-C₆-alkenyl,         C₂-C₆-alkynyl, C₁-C₆-alkoxy, phenyl-C₁-C₆-alkoxy, phenyl, phenyl         substituted with halogen, C₃-C₆-cycloalkyl,         C₃-C₆-halocycloalkyl, SO₂R⁸;     -   R⁸ C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl,         C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, phenyl; wherein the         phenyl moiety of R⁸ can be unsubstituted or substituted with one         or more radicals selected from halogen, C₁-C₄-alkoxy,         C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, heterocyclyl, phenyl;     -   and their agriculturally useful salts;

In addition, subject matter of the present invention is the use of isoxazolo[5,4-b]pyridines of formula I as herbicides, i.e. their use for controlling harmful plants.

The present invention also provides compositions comprising at least one isoxazolo[5,4-b]pyridine of formula I and auxiliaries customary for formulating crop protection agents.

The present invention furthermore provides a method for controlling unwanted vegetation, where a herbicidal effective amount of at least one isoxazolo[5,4-b]pyridine of formula I is allowed to act on plants, their seeds and/or their habitat. Application can be done before, during and/or after, preferably during and/or after, the emergence of the undesirable plants.

Moreover, the invention relates to processes for preparing isoxazolo[5,4-b]pyridines of formula I.

Further embodiments of the present invention are evident from the claims, the description and the examples. It is to be understood that the features mentioned above and still to be illustrated below of the subject matter of the invention can be applied not only in the combination given in each particular case but also in other combinations, without leaving the scope of the invention.

As used herein, the terms “controlling” and “combating” are synonyms.

As used herein, the terms “undesirable vegetation”, “weeds” and “harmful plants” are synonyms.

If the isoxazolo[5,4-b]pyridines of formula I as described herein are capable of forming geometrical isomers, for example E/Z isomers, it is possible to use both, the pure isomers and mixtures thereof, in the compositions according to the invention.

If the isoxazolo[5,4-b]pyridines of formula I as described herein have one or more centers of chirality and, as a consequence, are present as enantiomers or diastereomers, it is possible to use both, the pure enantiomers and diastereomers and their mixtures, in the compositions according to the invention.

The terms used for organic groups in the definition of the variables are, for example the expression “alkyl”, collective terms which represent the individual members of these groups of organic units.

The prefix C_(x)-C_(y) denotes the number of possible carbon atoms in the particular case.

halogen: fluorine, chlorine, bromine or iodine, especially fluorine, chlorine or bromine;

alkyl and the alkyl moieties of composite groups such as alkoxy, alkylamino, alkylthio, alkoxycarbonyl: saturated straight-chain or branched hydrocarbon radicals having 1 to 10 carbon atoms, preferably C₁-C₆-alkyl or C₁-C₄-alkyl, such as methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl and 1-ethyl-2-methylpropyl; heptyl, octyl, 2-ethylhexyl and positional isomers thereof; nonyl, decyl and positional isomers thereof; haloalkyl: straight-chain or branched alkyl groups having 1 to 10 carbon atoms (as mentioned above), preferably C₁-C₆-haloalkyl or C₁-C₄-haloalkyl, where some or all of the hydrogen atoms in these groups are replaced by halogen atoms as mentioned above. In one embodiment, the alkyl groups are substituted at least once or completely by a particular halogen atom, preferably fluorine, chlorine or bromine. In a further embodiment, the alkyl groups are partially or fully halogenated by different halogen atoms; in the case of mixed halogen substitutions, the combination of chlorine and fluorine is preferred. Particular preference is given to (C₁-C₃)-haloalkyl, more preferably (C₁-C₂)-haloalkyl, such as chloromethyl, bromomethyl, dichloromethyl, trichloromethyl, fluoromethyl, difluoromethyl, trifluoromethyl, chlorofluoromethyl, dichlorofluoromethyl, chlorodifluoromethyl, 1-chloroethyl, 1-bromoethyl, 1-fluoroethyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 2-chloro-2-fluoroethyl, 2-chloro-2,2-difluoroethyl, 2,2-dichloro-2-fluoroethyl, 2,2,2-trichloroethyl, pentafluoroethyl or 1,1,1-trifluoroprop-2-yl; alkenyl and also the alkenyl moieties in composite groups, such as alkenyloxy: unsaturated straight-chain or branched hydrocarbon radicals having 2 to 10 carbon atoms and one double bond in any position. According to the invention, it may be preferred to use small alkenyl groups, such as (C₂-C₆)-alkenyl; on the other hand, it may also be preferred to employ larger alkenyl groups, such as (C₅-C₈)-alkenyl. Examples of C₂-C₆-alkenyl groups are: ethenyl, 1-propenyl, 2-propenyl, 1-methylethenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-1-propenyl, 2-methyl-1-propenyl, 1-methyl-2-propenyl, 2-methyl-2-propenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-methyl-1-butenyl, 2-methyl-1-butenyl, 3-methyl-1-butenyl, 1-methyl-2-butenyl, 2-methyl-2-butenyl, 3-methyl-2-butenyl, 1-methyl-3-butenyl, 2-methyl-3-butenyl, 3-methyl-3-butenyl, 1,1-dimethyl-2-propenyl, 1,2-dimethyl-1-propenyl, 1,2-dimethyl-2-propenyl, 1-ethyl-1-propenyl, 1-ethyl-2-propenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl, 1-methyl-1-pentenyl, 2-methyl-1-pentenyl, 3-methyl-1-pentenyl, 4-methyl-1-pentenyl, 1-methyl-2-pentenyl, 2-methyl-2-pentenyl, 3-methyl-2-pentenyl, 4-methyl-2-pentenyl, 1-methyl-3-pentenyl, 2-methyl-3-pentenyl, 3-methyl-3-pentenyl, 4-methyl-3-pentenyl, 1-methyl-4-pentenyl, 2-methyl-4-pentenyl, 3-methyl-4-pentenyl, 4-methyl-4-pentenyl, 1,1-dimethyl-2-butenyl, 1,1-dimethyl-3-butenyl, 1,2-dimethyl-1-butenyl, 1,2-dimethyl-2-butenyl, 1,2-dimethyl-3-butenyl, 1,3-dimethyl-1-butenyl, 1,3-dimethyl-2-butenyl, 1,3-dimethyl-3-butenyl, 2,2-dimethyl-3-butenyl, 2,3-dimethyl-1-butenyl, 2,3-dimethyl-2-butenyl, 2,3-dimethyl-3-butenyl, 3,3-dimethyl-1-butenyl, 3,3-dimethyl-2-butenyl, 1-ethyl-1-butenyl, 1-ethyl-2-butenyl, 1-ethyl-3-butenyl, 2-ethyl-1-butenyl, 2-ethyl-2-butenyl, 2-ethyl-3-butenyl, 1,1,2-trimethyl-2-propenyl, 1-ethyl-1-methyl-2-propenyl, 1-ethyl-2-methyl-1-propenyl and 1-ethyl-2-methyl-2-propenyl; alkynyl and the alkynyl moieties in composite groups: straight-chain or branched hydrocarbon groups having 2 to 10 carbon atoms and one or two triple bonds in any position, for example C₂-C₆-alkynyl, such as ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-methyl-2-propynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, 4-pentynyl, 1-methyl-2-butynyl, 1-methyl-3-butynyl, 2-methyl-3-butynyl, 3-methyl-1-butynyl, 1,1-dimethyl-2-propynyl, 1-ethyl-2-propynyl, 1-hexynyl, 2-hexynyl, 3-hexynyl, 4-hexynyl, 5-hexynyl, 1-methyl-2-pentynyl, 1-methyl-3-pentynyl, 1-methyl-4-pentynyl, 2-methyl-3-pentynyl, 2-methyl-4-pentynyl, 3-methyl-1-pentynyl, 3-methyl-4-pentynyl, 4-methyl-1-pentynyl, 4-methyl-2-pentynyl, 1,1-dimethyl-2-butynyl, 1,1-dimethyl-3-butynyl, 1,2-dimethyl-3-butynyl, 2,2-dimethyl-3-butynyl, 3,3-dimethyl-1-butynyl, 1-ethyl-2-butynyl, 1-ethyl-3-butynyl, 2-ethyl-3-butynyl and 1-ethyl-1-methyl-2-propynyl; cycloalkyl and also the cycloalkyl moieties in composite groups: mono- or bicyclic saturated hydrocarbon groups having 3 to 10, in particular 3 to 6, carbon ring members. Examples for C₃-C₆-cycloalkyl are: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl. Examples of bicyclic radicals comprise bicyclo[2.2.1]heptyl, bicyclo[3.1.1]heptyl, bicyclo[2.2.2]octyl and bicyclo[3.2.1]octyl; halocycloalkyl and the halocycloalkyl moieties in composite groups: monocyclic saturated hydrocarbon groups having 3 to 10 carbon ring members (as mentioned above) in which some or all of the hydrogen atoms may be replaced by halogen atoms as mentioned above, in particular fluorine, chlorine and bromine; cycloalkenyl: monocyclic monounsaturated hydrocarbon groups having 3 to 10, 3 to 8, 3 to 6, preferably 5 to 6, carbon ring members, such as cyclopenten-1-yl, cyclopenten-3-yl, cyclohexen-1-yl, cyclohexen-3-yl, cyclohexen-4-yl and the like; alkoxy: an alkyl group as defined above, which is attached via an oxygen, preferably having 1 to 10, more preferably 1 to 6 or 1 to 4 carbon atoms. Examples are: methoxy, ethoxy, n-propoxy, 1-methylethoxy, butoxy, 1-methylpropoxy, 2-methylpropoxy or 1,1-dimethylethoxy, and also for example, pentoxy, 1-methylbutoxy, 2-methylbutoxy, 3-methylbutoxy, 1,1-dimethylpropoxy, 1,2-dimethylpropoxy, 2,2-dimethylpropoxy, 1-ethylpropoxy, hexoxy, 1-methylpentoxy, 2-methylpentoxy, 3-methylpentoxy, 4-methylpentoxy, 1,1-dimethylbutoxy, 1,2-dimethylbutoxy, 1,3-dimethylbutoxy, 2,2-dimethylbutoxy, 2,3-dimethylbutoxy, 3,3-dimethylbutoxy, 1-ethylbutoxy, 2-ethylbutoxy, 1,1,2-trimethylpropoxy, 1,2,2-trimethylpropoxy, 1-ethyl-1-methylpropoxy or 1-ethyl-2-methylpropoxy; haloalkoxy: alkoxy as defined above, where some or all of the hydrogen atoms in these groups are replaced by halogen atoms as described above under haloalkyl, in particular by fluorine, chlorine or bromine. Examples are OCH₂F, OCHF₂, OCF₃, OCH₂Cl, OCHCl₂, OCCl₃, chlorofluoromethoxy, dichlorofluoromethoxy, chlorodifluoromethoxy, 2-fluoroethoxy, 2-chloroethoxy, 2-bromoethoxy, 2-iodoethoxy, 2,2-difluoroethoxy, 2,2,2-trifluoroethoxy, 2-chloro-2-fluoroethoxy, 2-chloro-2,2-difluoroethoxy, 2,2-dichloro-2-fluoroethoxy, 2,2,2-trichloroethoxy, OC₂F₅, 2-fluoropropoxy, 3-fluoropropoxy, 2,2-difluoropropoxy, 2,3-difluoropropoxy, 2-chloropropoxy, 3-chloropropoxy, 2,3-dichloropropoxy, 2-bromopropoxy, 3-bromopropoxy, 3,3,3-trifluoropropoxy, 3,3,3-trichloropropoxy, OCH₂—C₂F₅, OCF₂—C₂F₅, 1-(CH₂F)-2-fluoroethoxy, 1-(CH₂Cl)-2-chloroethoxy, 1-(CH₂Br)-2-bromoethoxy, 4-fluorobutoxy, 4-chlorobutoxy, 4-bromobutoxy or nonafluorobutoxy; and also 5-fluoropentoxy, 5-chloropentoxy, 5-bromopentoxy, 5-iodopentoxy, undecafluoropentoxy, 6-fluorohexoxy, 6-chlorohexoxy, 6-bromohexoxy, 6-iodohexoxy or dodecafluorohexoxy; aryl: 6 to 10-membered, aromatic carbocycle with 6, 7, 8, 9 or 10 carbon atoms. Examples of preferred aryl are phenyl or naphthyl; heterocycle: 5-, 6-, 7-, 8-, 9- or 10-membered saturated, partially unsaturated or aromatic monocyclic ring or bicyclic ring system, which contains 1, 2, 3 or 4 heteroatoms from the group consisting of O, N and S as ring members, and may furthermore contain one or two CO, SO, SO₂ groups as ring members, where the heterocycle in question may be attached via a carbon atom or, if present, via a nitrogen atom. In particular:

-   -   a three, five- or six-membered saturated or partially         unsaturated heterocycle which comprises one, two, three or four         heteroatoms from the group consisting of O, N and S as ring         members: for example monocyclic saturated or partially         unsaturated heterocycles which, in addition to carbon ring         members, comprise one, two or three nitrogen atoms and/or one         oxygen or sulfur atom or one or two oxygen and/or sulfur atoms,         for example aziridine, oxirane, 2-tetrahydrofuranyl,         3-tetrahydrofuranyl, 2-tetrahydrothienyl, 3-tetrahydrothienyl,         2-pyrrolidinyl, 3-pyrrolidinyl, 3-isoxazolidinyl,         4-isoxazolidinyl, 5-isoxazolidinyl, 3-isothiazolidinyl,         4-isothiazolidinyl, 5-isothiazolidinyl, 3-pyrazolidinyl,         4-pyrazolidinyl, 5-pyrazolidinyl, 2-oxazolidinyl,         4-oxazolidinyl, 5-oxazolidinyl, 2-thiazolidinyl,         4-thiazolidinyl, 5-thiazolidinyl, 2-imidazolidinyl,         4-imidazolidinyl, 1,2,4-oxadiazolidin-3-yl,         1,2,4-oxadiazolidin-5-yl, 1,2,4-thiadiazolidin-3-yl,         1,2,4-thiadiazolidin-5-yl, 1,2,4-triazolidin-3-yl,         1,3,4-oxadiazolidin-2-yl, 1,3,4-thiadiazolidin-2-yl,         1,3,4-triazolidin-2-yl, 2,3-dihydrofur-2-yl,         2,3-dihydrofur-3-yl, 2,4-dihydrofur-2-yl, 2,4-dihydrofur-3-yl,         2,3-dihydrothien-2-yl, 2,3-dihydrothien-3-yl,         2,4-dihydrothien-2-yl, 2,4-dihydrothien-3-yl, 2-pyrrolin-2-yl,         2-pyrrolin-3-yl, 3-pyrrolin-2-yl, 3-pyrrolin-3-yl,         2-isoxazolin-3-yl, 3-isoxazolin-3-yl, 4-isoxazolin-3-yl,         2-isoxazolin-4-yl, 3-isoxazolin-4-yl, 4-isoxazolin-4-yl,         2-isoxazolin-5-yl, 3-isoxazolin-5-yl, 4-isoxazolin-5-yl,         2-isothiazolin-3-yl, 3-isothiazolin-3-yl, 4-isothiazolin-3-yl,         2-isothiazolin-4-yl, 3-isothiazolin-4-yl, 4-isothiazolin-4-yl,         2-isothiazolin-5-yl, 3-isothiazolin-5-yl, 4-isothiazolin-5-yl,         2,3-dihydropyrazol-1-yl, 2,3-dihydropyrazol-2-yl,         2,3-dihydropyrazol-3-yl, 2,3-dihydropyrazol-4-yl,         2,3-dihydropyrazol-5-yl, 3,4-dihydropyrazol-1-yl,         3,4-dihydropyrazol-3-yl, 3,4-dihydropyrazol-4-yl,         3,4-dihydropyrazol-5-yl, 4,5-dihydropyrazol-1-yl,         4,5-dihydropyrazol-3-yl, 4,5-dihydropyrazol-4-yl,         4,5-dihydropyrazol-5-yl, 2,3-dihydrooxazol-2-yl,         2,3-dihydrooxazol-3-yl, 2,3-dihydrooxazol-4-yl,         2,3-dihydrooxazol-5-yl, 3,4-dihydrooxazol-2-yl,         3,4-dihydrooxazol-3-yl, 3,4-dihydrooxazol-4-yl,         3,4-dihydrooxazol-5-yl, 3,4-dihydrooxazol-2-yl,         3,4-dihydrooxazol-3-yl, 3,4-dihydrooxazol-4-yl, 2-piperidinyl,         3-piperidinyl, 4-piperidinyl, 2-tetrahydropyranyl,         4-tetrahydropyranyl, 2-tetrahydrothienyl,         3-hexahydropyridazinyl, 4-hexahydropyridazinyl,         2-hexahydropyrimidinyl, 4-hexahydropyrimidinyl,         5-hexahydropyrimidinyl, 2-piperazinyl,         1,3,5-hexahydrotriazin-2-yl and 1,2,4-hexahydrotriazin-3-yl and         also the corresponding -ylidene radicals;     -   a seven-membered saturated or partially unsaturated heterocycle         which comprises one, two, three or four heteroatoms from the         group consisting of O, N and S as ring members: for example         mono- and bicyclic heterocycles having 7 ring members which, in         addition to carbon ring members, comprise one, two or three         nitrogen atoms and/or one oxygen or sulfur atom or one or two         oxygen and/or sulfur atoms, for example tetra- and         hexahydroazepinyl, such as 2,3,4,5-tetrahydro[1H]azepin-1-, -2-,         -3-, -4-, -5-, -6- or -7-yl, 3,4,5,6-tetrahydro[2H]azepin-2-,         -3-, -4-, -5-, -6- or -7-yl, 2,3,4,7-tetrahydro[1H]azepin-1-,         -2-, -3-, -4-, -5-, -6- or -7-yl,         2,3,6,7-tetrahydro[1H]azepin-1-, -2-, -3-, -4-, -5-, -6- or         -7-yl, hexahydroazepin-1-, -2-, -3- or -4-yl, tetra- and         hexahydrooxepinyl such as 2,3,4,5-tetrahydro[1H]oxepin-2-, -3-,         -4-, -5-, -6- or -7-yl, 2,3,4,7-tetrahydro[1H]oxepin-2-, -3-,         -4-, -5-, -6- or -7-yl, 2,3,6,7-tetrahydro[1H]oxepin-2-, -3-,         -4-, -5-, -6- or -7-yl, hexahydroazepin-1-, -2-, -3- or -4-yl,         tetra- and hexahydro-1,3-diazepinyl, tetra- and         hexahydro-1,4-diazepinyl, tetra- and hexahydro-1,3-oxazepinyl,         tetra- and hexahydro-1,4-oxazepinyl, tetra- and         hexahydro-1,3-dioxepinyl, tetra- and hexahydro-1,4-dioxepinyl         and the corresponding ylidene radicals;

a five- or six-membered aromatic heterocycle (=heteroaromatic radical) which contains one, two, three or four heteroatoms from the group consisting of oxygen, nitrogen and sulfur, for example 5-membered heteroaryl which is attached via carbon and contains one to three nitrogen atoms or one or two nitrogen atoms and one sulfur or oxygen atom as ring members, such as 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, 2-pyrrolyl, 3-pyrrolyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 3-isothiazolyl, 4-isothiazolyl, 5-isothiazolyl, 3-pyrazolyl, 4-pyrazolyl, 5-pyrazolyl, 2-oxazolyl, 4-oxazolyl, 5-oxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 2-imidazolyl, 4-imidazolyl, 1,2,4-oxadiazol-3-yl, 1,2,4-oxadiazol-5-yl, 1,2,4-thiadiazol-3-yl, 1,2,4-thiadiazol-5-yl, 1,2,4-triazol-3-yl, 1,3,4-oxadiazol-2-yl, 1,3,4-thiadiazol-2-yl and 1,3,4-triazol-2-yl; 5-membered heteroaryl which is attached via nitrogen and contains one to three nitrogen atoms as ring members, such as pyrrol-1-yl, pyrazol-1-yl, imidazol-1-yl, 1,2,3-triazol-1-yl and 1,2,4-triazol-1-yl; 6-membered heteroaryl, which contains one, two or three nitrogen atoms as ring members, such as pyridin-2-yl, pyridin-3-yl, pyridin-4-yl, 3-pyridazinyl, 4-pyridazinyl, 2-pyrimidinyl, 4-pyrimidinyl, 5-pyrimidinyl, 2-pyrazinyl, 1,3,5-triazin-2-yl and 1,2,4-triazin-3-yl;

The isoxazolo[5,4-b]pyridines of formula I may also be present in the form of the N-oxides and/or their agriculturally useful salts, the nature of the salt being, as a rule, immaterial. In general, suitable salts are the salts of those cations or the acid addition salts of those acids whose cations, or anions, respectively, do not adversely affect the herbicidal activity of the isoxazolo[5,4-b]pyridines of formula I.

Suitable cations are, in particular, ions of the alkali metals, preferably lithium, sodium or potassium, of the alkaline-earth metals, preferably calcium or magnesium, and of the transition metals, preferably manganese, copper, zinc or iron. Likewise, it is possible to use ammonium as the cation, where, if desired, one to four hydrogen atoms may be replaced by C₁-C₄-alkyl, hydroxy-C₁-C₄-alkyl, hydroxy-C₁-C₄-alkoxy-C₁-C₄-alkyl, phenyl or benzyl, preferably ammonium, dimethylammonium, diisopropylammonium, tetramethylammonium, tetrabutylammonium, 2-(2-hydroxyeth-1-oxy)eth-1-ylammonium, di(2-hydroxyeth-1-yl)ammonium, trimethylbenzylammonium. Others which are suitable are phosphonium ions, sulfonium ions, preferably tri(C₁-C₄-alkyl)sulfonium or sulfoxonium ions, preferably tri(C₁-C₄-alkyl)sulfoxonium.

Anions of useful acid addition salts are, mainly, chloride, bromide, fluoride, hydrogensulfate, sulfate, dihydrogenphosphate, hydrogenphosphate, nitrate, hydrogencarbonate, carbonate, hexafluorosilicate, hexafluorophosphate, benzoate and the anions of C₁-C₄-alkanoic acids, preferably formate, acetate, propionate, butyrate or trifluoracetate.

In general, isoxazolo[5,4-b]pyridines of formula I are suitable as herbicides.

Isoxazolo[5,4-b]pyridine compounds of formula I.a (formula I.a corresponds to formula I, wherein R¹ is hydrogen, X is OR⁴ and R⁴ is hydrogen)

or their agriculturally useful salts are particularly useful as herbicides.

Preferred embodiments of the isoxazolo[5,4-b]pyridine compounds of formula I.a are compounds 1.a.1 to 1.a.152 according to table 1, wherein each line of table 1 represents one compound of formula I:

TABLE 1 Isoxazolo[5,4-b]pyridine compounds 1.a.1 to 1.a.152 No. R² R³ I.a.1. CH₃ H I.a.2. CH₃ CH₃ I.a.3. CH₃ CH₂CH₃ I.a.4. CH₃ CH₂CH₂CH₃ I.a.5. CH₃ CH(CH₃)₂ I.a.6. CH₃ OCH(CH₃)₂ I.a.7. CH₃ CH₂C(CH₃)₃ I.a.8. CH₃ C(CH₃)₃ I.a.9. CH₃ OC(CH₃)₃ I.a.10. CH₃

I.a.11. CH₃

I.a.12. CH₃

I.a.13. CH₃

I.a.14. CH₃ C₆H₅ I.a.15. CH₃ 2-Cl—C₆H₄ I.a.16. CH₃ 2-F—C₆H₄ I.a.17. CH₃ 2-CH₃O—C₆H₄ I.a.18. CH₃ 2-CF₃—C₆H₄ I.a.19. CH₃ 3-Cl—C₆H₄ I.a.20. CH₃ 3-F—C₆H₄ I.a.21. CH₃ 3-CH₃O—C₆H₄ I.a.22. CH₃ 3-CF₃—C₆H₄ I.a.23. CH₃ 4-Cl—C₆H₄ I.a.24. CH₃ 4-F—C₆H₄ I.a.25. CH₃ 4-CH₃O—C₆H₄ I.a.26. CH₃ 4-CF₃—C₆H₄ I.a.27. CH₃ 2-Cl,3-Cl—C₆H₃ I.a.28. CH₃ 2-Cl,3-F—C₆H₃ I.a.29. CH₃ 2-F,3-Cl—C₆H₃ I.a.30. CH₃ 2-F,3-F—C₆H₃ I.a.31. CH₃ 2-Cl,4-Cl—C₆H₃ I.a.32. CH₃ 2-Cl,4-F—C₆H₃ I.a.33. CH₃ 2-F,4-Cl—C₆H₃ I.a.34. CH₃ 2-F,4-F—C₆H₃ I.a.35. CH₃ 3-Cl,5-Cl—C₆H₃ I.a.36. CH₃ 3-Cl,5-F—C₆H₃ I.a.37. CH₃ 3-F,5-Cl—C₆H₃ I.a.38. CH₃ 3-F,5-F—C₆H₃ I.a.39.

H I.a.40.

CH₃ I.a.41.

CH₂CH₃ I.a.42.

CH₂CH₂CH₃ I.a.43.

CH(CH₃)₂ I.a.44.

CH₂CH₂CH₂CH₃ I.a.45.

CH₂CH(CH₃)₂ I.a.46.

C(CH₃)₃ I.a.47.

CF₃ I.a.48.

I.a.49.

I.a.50.

I.a.51.

I.a.52.

C₆H₅ I.a.53.

2-Cl—C₆H₄ I.a.54.

2-F—C₆H₄ I.a.55.

2-CH₃O—C₆H₄ I.a.56.

2-CF₃—C₆H₄ I.a.57.

3-Cl—C₆H₄ I.a.58.

3-F—C₆H₄ I.a.59.

3-CH₃O—C₆H₄ I.a.60.

3-CF₃—C₆H₄ I.a.61.

4-Cl—C₆H₄ I.a.62.

4-F—C₆H₄ I.a.63.

4-CH₃O—C₆H₄ I.a.64.

4-CF₃—C₆H₄ I.a.65.

2-Cl,3-Cl—C₆H₃ I.a.66.

2-Cl,3-F—C₆H₃ I.a.67.

2-F,3-Cl—C₆H₃ I.a.68.

2-F,3-F—C₆H₃ I.a.69.

2-Cl,4-Cl—C₆H₃ I.a.70.

2-Cl,4-F—C₆H₃ I.a.71.

2-F,4-Cl—C₆H₃ I.a.72.

2-F,4-F—C₆H₃ I.a.73.

3-Cl,5-Cl—C₆H₃ I.a.74.

3-Cl,5-F—C₆H₃ I.a.75.

3-F,5-Cl—C₆H₃ I.a.76.

3-F,5-F—C₆H₃ I.a.77.

H I.a.78.

CH₃ I.a.79.

CH₂CH₃ I.a.80.

CH₂CH₂CH₃ I.a.81.

CH(CH₃)₂ I.a.82.

CH₂CH₂CH₂CH₃ I.a.83.

CH₂CH(CH₃)₂ I.a.84.

C(CH₃)₃ I.a.85.

CF₃ I.a.86.

I.a.87.

I.a.88.

I.a.89.

I.a.90.

C₆H₅ I.a.91.

2-Cl—C₆H₄ I.a.92.

2-F—C₆H₄ I.a.93.

2-CH₃O—C₆H₄ I.a.94.

2-CF₃—C₆H₄ I.a.95.

3-Cl—C₆H₄ I.a.96.

3-F—C₆H₄ I.a.97.

3-CH₃O—C₆H₄ I.a.98.

3-CF₃—C₆H₄ I.a.99.

4-Cl—C₆H₄ I.a.100.

4-F—C₆H₄ I.a.101.

4-CH₃O—C₆H₄ I.a.102.

4-CF₃—C₆H₄ I.a.103.

2-Cl,3-Cl—C₆H₃ I.a.104.

2-Cl,3-F—C₆H₃ I.a.105.

2-F,3-Cl—C₆H₃ I.a.106.

2-F,3-F—C₆H₃ I.a.107.

2-Cl,4-Cl—C₆H₃ I.a.108.

2-Cl,4-F—C₆H₃ I.a.109.

2-F,4-Cl—C₆H₃ I.a.110.

2-F,4-F—C₆H₃ I.a.111.

3-Cl,5-Cl—C₆H₃ I.a.112.

3-Cl,5-F—C₆H₃ I.a.113.

3-F,5-Cl—C₆H₃ I.a.114.

3-F,5-F—C₆H₃ I.a.115.

H I.a.116.

CH₃ I.a.117.

CH₂CH₃ I.a.118.

CH₂CH₂CH₃ I.a.119.

CH(CH₃)₂ I.a.120.

CH₂CH₂CH₂CH₃ I.a.121.

CH₂CH(CH₃)₂ I.a.122.

C(CH₃)₃ I.a.123.

CF₃ I.a.124.

I.a.125.

I.a.126.

I.a.127.

I.a.128.

C₆H₅ I.a.129.

2-Cl—C₆H₄ I.a.130.

2-F—C₆H₄ I.a.131.

2-CH₃O—C₆H₄ I.a.132.

2-CF₃—C₆H₄ I.a.133.

3-Cl—C₆H₄ I.a.134.

3-F—C₆H₄ I.a.135.

3-CH₃O—C₆H₄ I.a.136.

3-CF₃—C₆H₄ I.a.137.

4-Cl—C₆H₄ I.a.138.

4-F—C₆H₄ I.a.139.

4-CH₃O—C₆H₄ I.a.140.

4-CF₃—C₆H₄ I.a.141.

2-Cl,3-Cl—C₆H₃ I.a.142.

2-Cl,3-F—C₆H₃ I.a.143.

2-F,3-Cl—C₆H₃ I.a.144.

2-F,3-F—C₆H₃ I.a.145.

2-Cl,4-Cl—C₆H₃ I.a.146.

2-Cl,4-F—C₆H₃ I.a.147.

2-F,4-Cl—C₆H₃ I.a.148.

2-F,4-F—C₆H₃ I.a.149.

3-Cl,5-Cl—C₆H₃ I.a.150.

3-Cl,5-F—C₆H₃ I.a.151.

3-F,5-Cl—C₆H₃ I.a.152.

3-F,5-F—C₆H₃

In addition, the following isoxazolo[5,4-b]pyridine compounds of formula I are particularly useful as herbicides:

TABLE 2 Isoxazolo[5,4-b]pyridine compounds I.b.1 to I.b.152 The compounds 1.b.1 to 1.b.152, which differ from the isoxazolo[5,4-b]pyridine compounds I.a.1 to I.a.152 according to table 1 only regarding the variable R⁴, which is CH₃. I.b

TABLE 3 Isoxazolo[5,4-b]pyridine compounds I.c.1 to I.c.152 The compounds 1.c.1 to 1.c.152, which differ from the isoxazolo[5,4-b]pyridine compounds I.a.1 to I.a.152 according to table 1 only regarding the variable R⁴, which is CH₂OCH₃. I.c

TABLE 4 Isoxazolo[5,4-b]pyridine compounds I.d.1 to I.d.152 The compounds 1.d.1 to 1.d.152, which differ from the isoxazolo[5,4-b]pyridine compounds I.a.1 to I.a.152 according to table 1 only regarding the variable R⁴, which is CH₂CN. I.d

TABLE 5 Isoxazolo[5,4-b]pyridine compounds I.e.1 to I.e.152 The compounds 1.e.1 to 1.e.152, which differ from the isoxazolo[5,4-b]pyridine compounds I.a.1 to I.a.152 according to table 1 only regarding the variable R⁴, which is CH₂CH═CH₂. I.e

TABLE 6 Isoxazolo[5,4-b]pyridine compounds I.f.1 to I.f.152 The compounds 1.f.1 to 1.f.152, which differ from the isoxazolo[5,4-b]pyridine compounds I.a.1 to I.a.152 according to table 1 only regarding the variable R⁴, which is CH₂C≡CH. I.f

According to a preferred embodiment of the invention preference is also given to those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

R¹ is hydrogen, halogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl;

Particularly preferred are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein R¹ is hydrogen.

According to another preferred embodiment of the invention, preference is also given to those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl; and in particular to those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   R² is C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl;

Very particularly preferred are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein R² is C₃-C₆-cycloalkyl or C₃-C₆-halocycloalkyl; Most particularly preferred are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein is R² is cyclopropyl or 1-fluorocyclopropyl.

According to another preferred embodiment of the invention, preference is also given to those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   R³ is C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy, phenyl;     wherein the phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino,     N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl;

Particularly preferred are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein R³ is C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl, C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy;

According to another preferred embodiment of the invention, preference is also given to those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   X is OR⁴.

According to another preferred embodiment of the invention, preference is also given to those isoxazolo[5,4-b]pyridine compounds of formula I, wherein,

-   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl.

Particularly preferred are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein R⁴ is hydrogen, methyl, ethyl, n-propyl, i-propyl, n-butyl, 1-methylpropyl, 2-methylpropoyl, tert.-butyl; Most particularly preferred are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein is R⁴ is hydrogen;

According to another preferred embodiment of the invention, preference is also given to those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

X is SR⁵.

According to another preferred embodiment of the invention, preference is also given to those isoxazolo[5,4-b]pyridine compounds of formula I, wherein,

R⁵ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl.

Particularly preferred are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein R⁵ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, phenyl-C₁-C₆-alkyl; Most particularly preferred are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein is R⁵ is C₁-C₆-alkyl, phenyl-C₁-C₆-alkyl;

Particularly useful as herbicides are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   R¹ is hydrogen; -   R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl; -   R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,     C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-alkoxy-C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyloxy-C₁-C₆-alkyl, C₂-C₆-haloalkenyloxy-C₁-C₆-alkyl,     C₁-C₆-alkoxycarbonyl-C₁-C₆-alkyl, aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkyl-aminocarbonyl-C₁-C₆-alkyl,     N,N-di-(C₁-C₆-alkyl)-aminocarbonyl-C₁-C₆-alkyl,     [N—(C₃-C₆-cycloalkyl-C₁-C₆-alkyl),     N—(C₁-C₆-alkyl)]aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkoxy-aminocarbonyl-C₁-C₆-alkyl, C₂-C₆-alkenyl,     C₂-C₆-haloalkenyl, C₂-C₆-alkynyl-C₂-C₆-alkenyl, C₂-C₆-alkynyl,     C₂-C₆-haloalkynyl, heterocyclyl, phenyl, heterocyclylcarbonyl,     phenylcarbonyl, heterocyclylcarbonyl-C₁-C₆-alkyl,     phenylcarbonyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl,     phenyl-C₁-C₆-alkyl; wherein the phenyl and heterocyclyl moieties of     R⁴ and R⁵ can be unsubstituted or substituted with one or more     radicals selected from halogen, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, heterocyclyl,     phenyl;     and their agriculturally useful salts;

Particularly useful as herbicides are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   R¹ is hydrogen; -   R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl; -   R³ is C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl, C₁-C₆-alkoxy,     C₁-C₆-haloalkoxy, phenyl; wherein the phenyl moieties of R³ can be     unsubstituted or substituted with one or more radicals selected from     halogen, hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino,     C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-alkoxy-C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyloxy-C₁-C₆-alkyl, C₂-C₆-haloalkenyloxy-C₁-C₆-alkyl,     C₁-C₆-alkoxycarbonyl-C₁-C₆-alkyl, aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkyl-aminocarbonyl-C₁-C₆-alkyl,     N,N-di-(C₁-C₆-alkyl)-aminocarbonyl-C₁-C₆-alkyl,     [N—(C₃-C₆-cycloalkyl-C₁-C₆-alkyl),     N—(C₁-C₆-alkyl)]aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkoxy-aminocarbonyl-C₁-C₆-alkyl, C₂-C₆-alkenyl,     C₂-C₆-haloalkenyl, C₂-C₆-alkynyl-C₂-C₆-alkenyl, C₂-C₆-alkynyl,     C₂-C₆-haloalkynyl, heterocyclyl, phenyl, heterocyclylcarbonyl,     phenylcarbonyl, heterocyclylcarbonyl-C₁-C₆-alkyl,     phenylcarbonyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl,     phenyl-C₁-C₆-alkyl; wherein the phenyl and heterocyclyl moieties of     R⁴ and R⁵ can be unsubstituted or substituted with one or more     radicals selected from halogen, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, heterocyclyl,     phenyl;     and their agriculturally useful salts;

Particularly useful as herbicides are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   R¹ is hydrogen; -   R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl; -   R³ is C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl, C₁-C₆-alkoxy,     C₁-C₆-haloalkoxy, phenyl; wherein the phenyl moieties of R³ can be     unsubstituted or substituted with one or more radicals selected from     halogen, hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino,     C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl; is most preferably     hydrogen;     and their agriculturally useful salts;

Particularly useful as herbicides are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   R¹ is hydrogen; -   R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl; -   R³ is C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl, C₁-C₆-alkoxy,     C₁-C₆-haloalkoxy, phenyl; wherein the phenyl moieties of R³ can be     unsubstituted or substituted with one or more radicals selected from     halogen, hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino,     C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl; -   X is SR⁵; -   R⁵ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, phenyl-C₁-C₆-alkyl; is     most preferably C₁-C₆-alkyl, phenyl-C₁-C₆-alkyl;     and their agriculturally useful salts;

More particularly useful as herbicides are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   R¹ is hydrogen; -   R² is C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl; most preferably     cyclopropyl or 1-fluorocyclopropyl; -   R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,     C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₅)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-alkoxy-C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyloxy-C₁-C₆-alkyl, C₂-C₆-haloalkenyloxy-C₁-C₆-alkyl,     C₁-C₆-alkoxycarbonyl-C₁-C₆-alkyl, aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkyl-aminocarbonyl-C₁-C₆-alkyl,     N,N-di-(C₁-C₆-alkyl)-aminocarbonyl-C₁-C₆-alkyl,     [N—(C₃-C₆-cycloalkyl-C₁-C₆-alkyl),     N—(C₁-C₆-alkyl)]aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkoxy-aminocarbonyl-C₁-C₆-alkyl, C₂-C₆-alkenyl,     C₂-C₆-haloalkenyl, C₂-C₆-alkynyl-C₂-C₆-alkenyl, C₂-C₆-alkynyl,     C₂-C₆-haloalkynyl, heterocyclyl, phenyl, heterocyclylcarbonyl,     phenylcarbonyl, heterocyclylcarbonyl-C₁-C₆-alkyl,     phenylcarbonyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl,     phenyl-C₁-C₆-alkyl; wherein the phenyl and heterocyclyl moieties of     R⁴ and R⁵ can be unsubstituted or substituted with one or more     radicals selected from halogen, C₁-C₄-alkyl, C₁-C₄-alkoxy,     C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, heterocyclyl, phenyl; most     preferably hydrogen;     and their agriculturally useful salts;

More particularly useful as herbicides are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   R¹ is hydrogen; -   R² is C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl; most preferably     cyclopropyl or 1-fluorocyclopropyl; -   R³ is C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy, phenyl;     wherein the phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, alkoxycarbonyl,     C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl; most preferably     hydrogen;     and their agriculturally useful salts;

Most particularly useful as herbicides are those isoxazolo[5,4-b]pyridine compounds of formula I, wherein

-   R¹ is hydrogen; -   R² is cyclopropyl; -   R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,     C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen;     and their agriculturally useful salts;

While isoxazolo[5,4-b]pyridine compounds are know in the art, particular isoxazolo[5,4-b]pyridine compounds of formula I are novel. Accordingly, subject matter of the present invention are also isoxazolo[5,4-b]pyridine compounds of formula I

wherein

-   R¹ is hydrogen, halogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl; -   R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl; -   R³ hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,     C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl; -   and their agriculturally useful salts with the exception of     isoxazolo[5,4-b]pyridine compounds of formula I, wherein -   R¹ is hydrogen, R² is cyclopropyl, R³ is CH₃, X is OR⁴ and R⁴ is     hydrogen, C₁-C₆-alkyl, cyanomethyl, or 2-Cl-2-propen-1-yl; and -   R¹ is hydrogen, R² is cyclopropyl, R³ is CH₂C(CH₃)₃, (CH₂)₂CH₃,     CH(CH₃)₂, C(CH₃)₃, cyclopropyl, phenyl, 2-F-phenyl, 4-F-phenyl,     4-methylphenyl, 4-methoxyphenyl, 2-furan-yl,     1,3,5-trimethyl-1H-pyrazol-4-yl, 1-ethyl-5-methyl-1H-pyrazol-4-yl, X     is OR⁴ and R⁴ is hydrogen, methyl or ethyl; and -   R¹ is hydrogen, R² is methyl, R³ is CH₃, CH₂C(CH₃)₃, (CH₂)₂CH₃,     CH(CH₃)₂, C(CH₃)₃, cyclopropyl, phenyl, 4-methylphenyl,     4-methoxyphenyl, 3-methoxyphenyl, 4-fluorophenyl,     3,4-dichlorophenyl, 2-furan-yl, 1,3,5-trimethyl-1H-pyrazol-4-yl,     1-ethyl-5-methyl-1H-pyrazol-4-yl, X is OR⁴ and R⁴ is hydrogen,     methyl or ethyl; and -   R¹ is hydrogen, R² is ethyl, R³ is CH₃, (CH₂)₂CH₃, CH(CH₃)₂,     CH₂C(CH₃)₃, cyclopropyl, 1,3,5-trimethyl-1H-pyrazol-4-yl, X is OR⁴     and R⁴ is hydrogen, methyl or ethyl; and -   R¹ is hydrogen, R² is i-propyl, R³ is CH₃, CH₂C(CH₃)₃, (CH₂)₂CH₃,     CH(CH₃)₂, C(CH₃)₃, cyclopropyl, phenyl, 3-methoxyphenyl, 2-furan-yl;     X is OR⁴ and R⁴ is hydrogen, methyl or ethyl; and -   R¹ is chlorine, R² is methyl, cyclopropyl, R³ is methyl, X is OR⁴     and R⁴ is hydrogen or methyl.

Subject matter of the present invention are also isoxazolo[5,4-b]pyridine compounds of formula I,

wherein

-   R¹ is hydrogen; -   R² is cyclopropyl; -   R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,     C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₅)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino,     C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-alkoxy-C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyloxy-C₁-C₆-alkyl, C₂-C₆-haloalkenyloxy-C₁-C₆-alkyl,     C₁-C₆-alkoxycarbonyl-C₁-C₆-alkyl, aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkyl-aminocarbonyl-C₁-C₆-alkyl,     N,N-di-(C₁-C₆-alkyl)-aminocarbonyl-C₁-C₆-alkyl,     [N—(C₃-C₆-cycloalkyl-C₁-C₆-alkyl),     N—(C₁-C₆-alkyl)]aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkoxy-aminocarbonyl-C₁-C₆-alkyl, C₂-C₆-alkenyl,     C₂-C₆-haloalkenyl, C₂-C₆-alkynyl-C₂-C₆-alkenyl, C₂-C₆-alkynyl,     C₂-C₆-haloalkynyl, heterocyclyl, phenyl, heterocyclylcarbonyl,     phenylcarbonyl, heterocyclylcarbonyl-C₁-C₆-alkyl,     phenylcarbonyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl,     phenyl-C₁-C₆-alkyl; wherein the phenyl and heterocyclyl moieties of     R⁴ can be unsubstituted or substituted with one or more radicals     selected from halogen, C₁-C₄-alkyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy,     C₁-C₄-alkoxycarbonyl, heterocyclyl, phenyl; most preferably     hydrogen;     and their agriculturally useful salts; with the exception of:     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(2,3-dihydro-1H-indol-1-yl)-1-methyl-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-fluorophenyl)-methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-[4-(methoxycarbonyl)-3,5-dimethyl-1H-pyrrol-2-yl]-1-methyl-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(3-methyl-2-quinoxalinyl)methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(2-methoxy-4-methylphenyl)-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-[5-(2-furanyl)-3-isoxazolyl]methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(4-ethoxyphenoxy)ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-1-(5-phenyl-1,3,4-oxadiazol-2-yl)ethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(5-ethyl-2-thienyl)-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-chloro-2-propen-1-yl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(3,4-dihydro-1(2H)-quinolinyl)-1-methyl-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(3,4-dimethoxyphenyl)-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(3,4-dihydro-2(1H)-isoquinolinyl)-1-methyl-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-ethyl-5-methyl-1H-pyrazol-4-yl)-, methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(4-methoxyphenyl)-1-methyl-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-[2-(3-thienyl)-4-thiazolyl]methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-fluorophenyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-pyridinylmethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(3-fluoro-4-methoxyphenyl)-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(4-fluorophenyl)-1-methyl-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-oxo-2-(pentylamino)ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(5-bromo-2-methoxyphenyl)methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-1-methyl-2-oxo-2-phenylethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-1-methyl-2-[(1-methylethyl)amino]-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methoxyphenyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(6-chloro-3-pyridinyl)methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-amino-1-methyl-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(2-chloro-6-fluorophenyl)methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(2-bromophenyl)-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(1,1-dimethylethoxy)-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-[2,5-dimethyl-1-(3-methylbutyl)-1H-pyrrol-3-yl]-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(2,4-dihydroxyphenyl)-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-[2-(difluoromethoxy)-5-methylphenyl]-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(3-methyl-2-benzofuranyl)-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(2-methoxyphenyl)-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(5-methyl-2-thienyl)-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-oxo-2-(2,3,4,5-tetramethylphenyl)ethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-[5-(2-thienyl)-1,3,4-oxadiazol-2-yl]methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methylphenyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(3-fluoro-4-methoxyphenyl)methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(7-methyl-4-oxo-4H-pyrido[1,2-a]pyrimidin-2-yl)methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(4-methoxyphenyl)ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(1-butyl-1H-tetrazol-5-yl)methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(1H-indol-3-yl)-1-methyl-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-benzoxazolylmethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-1-methylethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-[(1-methylbutyl)amino]-2-oxoethyl         ester;

-   -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-cyanomethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-[3-(methoxycarbonyl)-2-furanyl]methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(3-methyl-5-isoxazolyl)methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(5-chloro-1,2,3-thiadiazol-4-yl)methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,1-dimethylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-[(1,5-dimethylhexyl)amino]-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-phenyl-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(2-oxo-1-imidazolidinyl)-2-oxoethyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-methoxy-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-(2,4-dimethoxyphenyl)-2-oxoethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-4-(2-oxo-1-pyrrolidinyl)phenyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl-,         methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl-,         ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(3,5-dimethyl-4-isoxazolyl)methyl ester;

-   -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-[3-(2-thienyl)-1,2,4-oxadiazol-5-yl]methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl)-, methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2,3-dichlorophenyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(8-methylimidazo[1,2-a]pyridin-2-yl)methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-(2-ethyl-4-thiazolyl)methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2,2-dimethylpropyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2,2-dimethylpropyl)-, ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-propyl-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-propyl-, ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-furanyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-furanyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-furanyl)-, ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-phenyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-phenyl-, ethyl ester     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-, ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-methylethyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-methylethyl)-, ethyl ester;

In a preferred embodiment, subject matter of the present invention are also isoxazolo[5,4-b]pyridine compounds of formula I

wherein

-   R¹ is hydrogen; -   R² is cyclopropyl; -   R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,     C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino,     N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl;     and their agriculturally useful salts; with the exception of:     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-fluorophenyl)-methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-chloro-2-propen-1-yl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-ethyl-5-methyl-1H-pyrazol-4-yl)-, methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-fluorophenyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methoxyphenyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methylphenyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-1-methylethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-cyanomethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,1-dimethylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-phenyl-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl-,         methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl-,         ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl)-, methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2,2-dimethylpropyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2,2-dimethylpropyl)-, ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-propyl-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-propyl-, ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-furanyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-furanyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-furanyl)-, ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-phenyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-phenyl-, ethyl ester     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-, ethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-methylethyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-methylethyl)-, ethyl ester;

Additionally, subject matter of the present invention are also isoxazolo[5,4-b]pyridine compounds of formula I

wherein

-   R¹ is halogen; -   R² hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl; -   R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,     C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₅)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino,     C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl; -   X is OR⁴ -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-alkoxy-C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyloxy-C₁-C₆-alkyl, C₂-C₆-haloalkenyloxy-C₁-C₆-alkyl,     C₁-C₆-alkoxycarbonyl-C₁-C₆-alkyl, aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkyl-aminocarbonyl-C₁-C₆-alkyl,     N,N-di-(C₁-C₆-alkyl)-aminocarbonyl-C₁-C₆-alkyl,     [N—(C₃-C₆-cycloalkyl-C₁-C₆-alkyl),     N—(C₁-C₆-alkyl)]aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkoxy-aminocarbonyl-C₁-C₆-alkyl, C₂-C₆-alkenyl,     C₂-C₆-haloalkenyl, C₂-C₆-alkynyl-C₂-C₆-alkenyl, C₂-C₆-alkynyl,     C₂-C₆-haloalkynyl, heterocyclyl, phenyl, heterocyclylcarbonyl,     phenylcarbonyl, heterocyclylcarbonyl-C₁-C₆-alkyl,     phenylcarbonyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl,     phenyl-C₁-C₆-alkyl; wherein the phenyl and heterocyclyl moieties of     R⁴ and R⁵ can be unsubstituted or substituted with one or more     radicals selected from halogen, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, heterocyclyl,     phenyl; most preferably hydrogen;     and their agriculturally useful salts; with the exception of:     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         5-chloro-6-cyclopropyl-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         5-chloro-6-cyclopropyl-3-methyl-, methyl ester; -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 5-chloro-3,5-dimethyl;

Additionally, subject matter of the present invention are also isoxazolo[5,4-b]pyridine compounds of formula I

wherein

-   R¹ is hydroxyl, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl,     C₂-C₆-alkenyl, C₂-C₆-alkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     phenyl, phenyl-C₁-C₄-alkyl; -   R² is cyclopropyl; -   R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,     C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino,     C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl; -   X is OR⁴ -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-alkoxy-C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyloxy-C₁-C₆-alkyl, C₂-C₆-haloalkenyloxy-C₁-C₆-alkyl,     C₁-C₆-alkoxycarbonyl-C₁-C₆-alkyl, aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkyl-aminocarbonyl-C₁-C₆-alkyl,     N,N-di-(C₁-C₆-alkyl)-aminocarbonyl-C₁-C₆-alkyl,     [N—(C₃-C₆-cycloalkyl-C₁-C₆-alkyl),     N—(C₁-C₆-alkyl)]-aminocarbonyl-C₁-C₆-alkyl,     C₁-C₆-alkoxy-aminocarbonyl-C₁-C₆-alkyl, C₂-C₆-alkenyl,     C₂-C₆-haloalkenyl, C₂-C₆-alkynyl-C₂-C₆-alkenyl, C₂-C₆-alkynyl,     C₂-C₆-haloalkynyl, heterocyclyl, phenyl, heterocyclylcarbonyl,     phenylcarbonyl, heterocyclylcarbonyl-C₁-C₆-alkyl,     phenylcarbonyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl,     phenyl-C₁-C₆-alkyl; wherein the phenyl and heterocyclyl moieties of     R⁴ and R⁵ can be unsubstituted or substituted with one or more     radicals selected from halogen, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, heterocyclyl,     phenyl; most preferably hydrogen;     -   and their agriculturally useful salts.

Additionally, subject matter of the present invention are also isoxazolo[5,4-b]pyridine compounds of formula I

wherein

-   R¹ is hydrogen, halogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl; -   R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl; -   R³ hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl,     C₁-C₄-alkyl-C₃-C₆-cycloalkyl-C₃-C₆-cycloalkenyl,     C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₁-C₄-haloalkyl, C₃-C₆-cycloalkyl,     C₂-C₆-alkenyl, C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy,     C₁-C₄-alkoxycarbonyl, C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino,     N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl; -   X is OR⁴, SR⁵; -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl,     C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl,     C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl;     and their agriculturally useful salts; with the exception of:     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-fluorophenyl)-methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-2-chloro-2-propen-1-yl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-ethyl-5-methyl-1H-pyrazol-4-yl)-, methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-fluorophenyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methoxyphenyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methylphenyl)-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-1-methylethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl-cyanomethyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,1-dimethylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-phenyl-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl-,         methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl)-, methyl         ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-furanyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-phenyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dimethyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(1,1-dimethylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-cyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-phenyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(4-methylphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(3-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(4-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(4-fluorophenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(3,4-dichlorophenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(2-furanyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(1-ethyl-5-methyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-ethyl-3-(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-ethyl-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-ethyl-3-cyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-ethyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         3,6-bis(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-(1,1-dimethylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-cyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-phenyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-(3-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-(2-furanyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         5-chloro-6-cyclopropyl-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         5-chloro-6-cyclopropyl-3-methyl-, methyl ester;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         5-chloro-3,5-dimethyl;

Additionally, subject matter of the present invention are also isoxazolo[5,4-b]pyridine compounds of formula I

wherein

-   R¹ is hydrogen, halogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl; -   R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl,     C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl; -   R³ hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl,     C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl,     C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl,     C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl,     C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl,     C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl,     heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl,     C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy,     C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino,     N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, phenyl; wherein the     heterocyclyl and phenyl moieties of R³ can be unsubstituted or     substituted with one or more radicals selected from halogen,     hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkyl,     C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl,     C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl,     C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino,     C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, phenyl; -   X is OR⁴; -   R⁴ is hydrogen;     and their agriculturally useful salts; with the exception of:     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1,1-dimethylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(4-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(2-furanyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-phenyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-cyclopropyl-3-(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dimethyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(1,1-dimethylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-cyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-phenyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(4-methylphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(3-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(4-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(4-fluorophenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(3,4-dichlorophenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(2-furanyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-methyl-3-(1-ethyl-5-methyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-ethyl-3-(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-ethyl-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-ethyl-3-cyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-ethyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-propyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         3,6-bis(1-methylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-(1,1-dimethylethyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-(2,2-dimethylpropyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-cyclopropyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-phenyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-(3-methoxyphenyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         6-(1-methylethyl)-3-(2-furanyl);     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         5-chloro-6-cyclopropyl-3-methyl;     -   Isoxazolo[5,4-b]pyridine-4-carboxylic acid,         5-chloro-3,5-dimethyl;

The isoxazolo[5,4-b]pyridines of formula I according to the invention can be prepared by standard processes of organic chemistry, for example by the following processes:

A compound of formula (C), where R¹ is C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl or phenyl-C₁-C₆-alkyl, can be prepared by adding a compound of formula (B), where Z is a halogen, in an inert organic solvent at a temperature from −100° C. to 30° C., preferably at a temperature from −80° C. to 0° C., most preferably at −78° C., to a compound of formula (A) under an inert gas atmosphere such as argon or nitrogen. The reaction mixture is worked up in a customary manner, for example by mixing with water, separation of the phases, extraction and, if appropriate, chromatographic purification of the crude product, preferably by extraction.

Suitable solvents are aliphatic hydrocarbons such as pentane, hexane, cyclohexane and mixtures of C₅-C₈-alkanes, aromatic hydrocarbons such as toluene, o-, m- and p-xylene, halogenated hydrocarbons such as dichloromethane, 1,2-dichloroethane, chloroform and chlorobenzene, ethers such as diethyl-ether, diisopropyl-ether, tert.-butylmethylether, dioxane, anisole and tetrahydrofuran, nitriles such as acetonitrile and propionitrile, as well as dimethylsulfoxide, dimethylformamide and N,N-dimethylacetamide or N-methylpyrrolidone.

Particular preference is given to tetrahydrofuran and diethyl ether. It is also possible to use mixtures of the solvents mentioned.

The compounds of formula (A) are known from the literature [Duncia, John V et al. Bioorganic & Medicinal Chemistry Letters 2008, 18(2), 576-585, and Gao, S. et al. Journal of the American Chemical Society 2010, 132(1), 371-383] or they can be prepared in accordance with the literature cited and/or are commercially available.

The compounds of formula (B) are commercially available.

A compound of formula (C), where R² is 1-fluorocyclopropyl and R¹ is hydrogen is known from the literature [DE 4206917].

A compound of formula (E), where R⁴ is C₁-C₆-alkyl and R¹ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl or phenyl-C₁-C₆-alkyl may be prepared by treating a mixture of compounds (D) and (C) with a suitable base. The reaction is conducted in an inert organic solvent at a temperature from −100° C. to 100° C., preferably at a temperature from 0° C. to 80° C. The reaction mixture is worked up in a customary manner, for example by mixing with water, separation of the phases, extraction and, if appropriate, chromatographic purification of the crude product.

Suitable bases are in general inorganic compounds such as alkali metal and alkaline earth metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide, alkali metal and alkaline earth metal hydrides such as lithium hydride, sodium hydride, potassium hydride and calcium hydride, alkali metal and alkaline earth metal carbonates such as lithium carbonate, potassium carbonate and calcium carbonate, as well as alkali metal bicarbonates such as sodium bicarbonate, alkali metal and alkaline earth metal alkoxides such as sodium methoxide, sodium ethoxide, potassium ethoxide, potassium tert-butoxide, potassium tert-pentoxide and dimethoxymagnesium, and furthermore organic bases, such as tertiary amines such as trimethylamine, triethylamine, diisopropylethylamine and N-methylpiperidine, pyridine, substituted pyridines such as collidine, lutidine, N-methylmorpholine and 4-dimethylaminopyridine and also bicyclic amines.

Particular preference is given to sodium methoxide and sodium ethoxide.

The bases are generally employed in equimolar amounts or in excess.

Suitable solvents are ethers such as diethyl ether, diisopropyl ether, tert.-butyl methylether, dioxane, anisole and tetrahydrofuran, nitriles such as acetonitrile and propionitrile, alkoholes such as methanol, ethanol, n-propanol, isopropanol, n-butanol and tert.-butanol, as well as dimethylsulfoxide, dimethylformamide and N,N-dimethylacetamide or N-methylpyrrolidone.

Particular preference is given to methanol or ethanol. It is also possible to use mixtures of the solvents mentioned.

Suitable methods required for the preparation of compound of formula (E) are known from the literature [Brecker, L. et al., New J. Chem., 1999, 23, 437-446]. The substrates required for the preparation of compound of formula (E) are commercially available

A compound of formula (E) where R¹ is halogen can be prepared according to suitable methods known from the literature [Cao, L. et al. Synlett 2009, 9, 1445-1448; Still, I. W. J. et al. Journal of Organic Chemistry 1981, 46(24), 4911-14 and Banks, R. E. et al. Journal of the Chemical Society, Chemical Communications 1994, 3, 343-344].

A compound of formula (G) can be prepared by mixing compound of formula (E) and compound of formula (F) in suitable solvent at a temperature of between 65° C. and 120° C., most preferably at 118° C. After the reaction is completed the reaction mixture is poured into ice/water. The solid formed is collected by filtration and dried under high vacuum.

Suitable solvents are

alkoholes such as methanol, ethanol, n-propanol, isopropanol, n-butanol and tert.-butanol, water, carboxylic acids, such as formic acid, glacial acetic acid, as well as dimethylsulfoxide, dimethylformamide and N,N-dimethylacetannide or N-methylpyrrolidone.

Particular preference is given to glacial acetic acid.

It is also possible to use mixtures of the solvents mentioned.

Similar methods are described, for example, Petrosyan, V. A. et al. Russ. Chem. Bull., Int. Ed., 2007, 56, 2186-2188.

Suitable methods required for the preparation of compound of formula (F) are known from the literature [Scott, K. R. European Journal of Medicinal Chemistry 2002, 37, 635-648, Mitsuhashi, K. Journal of Heterocyclic Chemistry, 1986, 23(5), 1535-8], EP 0220947, WO 2008034008, Dines, M. B. Tetrahedron Letters 1969, 54, 4817-4819; Koichi, M. Nitriles. IV. Synthesis of isoxazoles and pyrazoles from some three-carbon nitriles, Takeda Kenkyushoho 1971, 30(3), 475-92. Some of the compounds of formula (F) are commercially available.

A compound of formula (G) where R¹ is hydroxyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy can be prepared from a compound of formula (G) where R¹ is halogen according to suitable methods known from the literature, for example: Dejardin, J. V. et. al. Bulletin de la Societe Chimique de France 1976, 3-4, Pt. 2, 530-532, Ouyang, X. et. al. Bioorganic & Medicinal Chemistry Letters 2005, 15(23), 5154-5159 and Magee, T. V. et. al. Journal of Medicinal Chemistry 2009, 52(23), 7446-7457. A compound of formula (G) where R¹ is hydrogen and R³ is halogen can be prepared by mixing a compound of formula (G) where R¹ is hydrogen and R³ is OH with pyridine hydrohalide, acide (most preferably H₃PO₄) and phosphoroxyhalide and stirring it at a temperature between 50° C. and 120° C., most preferably at 90° C. for 1-5 h. The excess of phosphoroxyhalide is evaporated under high vacuum. The reaction mixture is worked up in a customary manner, for example by adding a suitable solvent and aqueus solution of alkali metal bicarbonate, separation of the phases, extraction and, if appropriate, chromatographic purification of the crude product.

Suitable solvents are ethyl acetate, dichloromethane, diethyl ether, chloroform, tertbuthylmethyl ether, diisopropyl ether. Suitable alkali metal bicarbonates are sodium bicarbonate, potassium bicarbonate, calcium bicarbonate.

A compound of formula (G) where R¹ is hydrogen and R³ is C₁-C₆-alkoxy can be prepared by adding a C₁-C₆-alkyl alcohol and a compound of formula (G) where R¹ is hydrogen and R³ is OH to the previously prepared stirred solution of di-C₁-C₆-alkyl azodicarboxylate and triarylphosphine (most preferably triphenylphosphine) in a suitable solvent (preferably tetrahydrofuran) at a temperature between −20° C. and 25° C., most preferably at 0° C. The reaction is conducted at a temperature between −20° C. to 100° C., preferably at a temperature between 40° C. to 80° C. The reaction mixture is worked up in a customary manner, for example by removing the solvent under vacuum and chromatographic purification of the crude product.

Suitable solvents are ethers such as diethyl-ether, diisopropyl-ether, tert.-butylmethylether, dioxane, anisole and tetrahydrofuran. Particular preference is given to tetrahydrofuran and diethyl ether. It is also possible to use mixtures of the solvents mentioned.

A compound of formula (H) can be prepared from a compound of formula (G) by hydrolysis in a presence of a suitable acid or base catalyst in a suitable solvent at temperatures between 0° C. and 80° C., most preferably at 25° C., under conventional heating or under microwave irradiation [see, for example, Carrigan, C. N. J. Med. Chem. 2002, 45, 2260-2276 and Ghosh, P. Journal of Teaching and Research in Chemistry 2008, 15(2), 54-57].

Suitable acid catalyst are:

anorganic acids like hydrofluoric acid, hydrochloric acid, hydrobromic acid, perchloric acid, sulphuric acid.

Particular preference is given to hydrochloric acid and sulphuric acid.

The acids are generally employed in catalytic amounts, however they can also be employed in equimolar amounts or in excess.

Suitable base catalyst are:

alkali metal and alkaline earth metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and calcium hydroxide.

Particular preference is given to metal hydroxides such as sodium hydroxide.

The bases are generally employed in catalytic amounts, however they can also be employed in equimolar amounts or in excess.

Suitable solvents are ethers such as diethyl ether, diisopropyl ether, tert.-butyl methylether, dioxane, anisole and tetrahydrofuran, water, alkoholes such as methanol, ethanol, n-propanol, isopropanol, n-butanol and tert.-butanol, as well as dimethylsulfoxide.

Particular preference is given to tetrahydrofuran.

It is also possible to use mixtures of the solvents mentioned.

A compound of formula (H) can be esterified, thioesterified, transformed to an amide or an acid halide, preferably acid chloride, of a compound of formula (I) where X is OR⁴ (see, for example, Arnab, P. et. al. Angewandte Chemie, International Edition 2010, 49(8), 1492-1495), SR⁵ (see, for example, Silvestri, M. A. et. al. Journal of Medicinal Chemistry 2004, 47(12), 3149-3162), NR⁶R⁷ (see, for example, Kuhn, B. et. al. Journal of Medicinal Chemistry 2010, 53(6), 2601-2611) under standard conditions.

The isoxazolo[5,4-b]pyridines of formula I are suitable as herbicides. They are suitable as such or as an appropriately formulated composition (herbicidal composition). As used in this application, the terms “formulated composition” and “herbicidal composition” are synonyms.

The herbicidal compositions comprising the isoxazolo[5,4-b]pyridines of formula I control vegetation on non-crop areas very efficiently, especially at high rates of application. They act against broad-leaved weeds and grass weeds in crops such as wheat, rice, maize, soya and cotton without causing any significant damage to the crop plants. This effect is mainly observed at low rates of application.

Depending on the application method in question, the isoxazolo[5,4-b]pyridines of formula I or compositions comprising them can additionally be employed in a further number of crop plants for eliminating undesirable plants. Examples of suitable crops are the following:

Allium cepa, Ananas comosus, Arachis hypogaea, Asparagus officinalis, Avena sativa, Beta vulgaris spec. altissima, Beta vulgaris spec. rapa, Brassica napus var. napus, Brassica napus var. napobrassica, Brassica rapa var. silvestris, Brassica oleracea, Brassica nigra, Camellia sinensis, Carthamus tinctorius, Carya illinoinensis, Citrus limon, Citrus sinensis, Coffea arabica (Coffea canephora, Coffea liberica), Cucumis sativus, Cynodon dactylon, Daucus carota, Elaeis guineensis, Fragaria vesca, Glycine max, Gossypium hirsutum, (Gossypium arboreum, Gossypium herbaceum, Gossypium vitifolium), Helianthus annuus, Hevea brasiliensis, Hordeum vulgare, Humulus lupulus, Ipomoea batatas, Juglans regia, Lens culinaris, Linum usitatissimum, Lycopersicon lycopersicum, Malus spec., Manihot esculenta, Medicago sativa, Musa spec., Nicotiana tabacum (N. rustica), Olea europaea, Oryza sativa, Phaseolus lunatus, Phaseolus vulgaris, Picea abies, Pinus spec., Pistacia vera, Pisum sativum, Prunus avium, Prunus persica, Pyrus communis, Prunus armeniaca, Prunus cerasus, Prunus dulcis and Prunus domestica, Ribes sylvestre, Ricinus communis, Saccharum officinarum, Secale cereale, Sinapis alba, Solanum tuberosum, Sorghum bicolor (S. vulgare), Theobroma cacao, Trifolium pratense, Triticum aestivum, Triticale, Triticum durum, Vicia faba, Vitis vinifera and Zea mays.

Preferred crops are the following: Arachis hypogaea, Beta vulgaris spec. altissima, Brassica napus var. napus, Brassica oleracea, Citrus limon, Citrus sinensis, Coffea arabica (Coffea canephora, Coffea liberica), Cynodon dactylon, Glycine max, Gossypium hirsutum, (Gossypium arboreum, Gossypium herbaceum, Gossypium vitifolium), Helianthus annuus, Hordeum vulgare, Juglans regia, Lens culinaris, Linum usitatissimum, Lycopersicon lycopersicum, Malus spec., Medicago sativa, Nicotiana tabacum (N. rustica), Olea europaea, Oryza sativa, Phaseolus lunatus, Phaseolus vulgaris, Pistacia vera, Pisum sativum, Prunus dulcis, Saccharum officinarum, Secale cereale, Solanum tuberosum, Sorghum bicolor (S. vulgare), Triticale, Triticum aestivum, Triticum durum, Vicia faba, Vitis vinifera and Zea mays.

The isoxazolo[5,4-b]pyridines of formula I according to the invention can also be used in genetically modified plants. The term “genetically modified plants” is to be understood as plants, which genetic material has been modified by the use of recombinant DNA techniques in a way that under natural circumstances it cannot readily be obtained by cross breeding, mutations or natural recombination. Typically, one or more genes have been integrated into the genetic material of a genetically modified plant in order to improve certain properties of the plant. Such genetic modifications also include but are not limited to targeted post-transtional modification of protein(s), oligo- or poly-peptides e.g. by glycosylation or polymer additions such as prenylated, acetylated or farnesylated moieties or PEG moieties.

Plants that have been modified by breeding, mutagenesis or genetic engineering, e.g. have been rendered tolerant to applications of specific classes of herbicides, such as auxin herbicides such as dicamba or 2,4-D; bleacher herbicides such as hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors or phytoene desaturase (PDS) inhibitors; acetolactate synthase (ALS) inhibitors such as sulfonyl ureas or imidazolinones; enolpyruvyl shikimate 3-phosphate synthase (EPSP) inhibitors such as glyphosate; glutamine synthetase (GS) inhibitors such as glufosinate; protoporphyrinogen-IX oxidase inhibitors; lipid biosynthesis inhibitors such as acetyl CoA carboxylase (ACCase) inhibitors; or oxynil (i. e. bromoxynil or ioxynil) herbicides as a result of conventional methods of breeding or genetic engineering; furthermore, plants have been made resistant to multiple classes of herbicides through multiple genetic modifications, such as resistance to both glyphosate and glufosinate or to both glyphosate and a herbicide from another class such as ALS inhibitors, HPPD inhibitors, auxin herbicides, or ACCase inhibitors. These herbicide resistance technologies are, for example, described in Pest Management Science 61, 2005, 246; 61, 2005, 258; 61, 2005, 277; 61, 2005, 269; 61, 2005, 286; 64, 2008, 326; 64, 2008, 332; Weed Science 57, 2009, 108; Australian Journal of Agricultural Research 58, 2007, 708; Science 316, 2007, 1185; and references quoted therein. Several cultivated plants have been rendered tolerant to herbicides by conventional methods of breeding (mutagenesis), e.g. Clearfield® summer rape (Canola, BASF SE, Germany) being tolerant to imidazolinones, e.g. imazamox, or ExpressSun® sunflowers (DuPont, USA) being tolerant to sulfonyl ureas, e.g. tribenuron. Genetic engineering methods have been used to render cultivated plants such as soybean, cotton, corn, beets and rape, tolerant to herbicides such as glyphosate, imidazolinones and glufosinate, some of which are under development or commercially available under the brands or trade names RoundupReady® (glyphosate tolerant, Monsanto, USA), Cultivance® (imidazolinone tolerant, BASF SE, Germany) and LibertyLink® (glufosinate tolerant, Bayer CropScience, Germany).

Furthermore, plants are also covered that are by the use of recombinant DNA techniques capable to synthesize one or more insecticidal proteins, especially those known from the bacterial genus Bacillus, particularly from Bacillus thuringiensis, such as ä-endotoxins, e.g. CryIA(b), CryIA(c), CryIF, CryIF(a2), CryIIA(b), CryIIIA, CryIIIB(b1) or Cry9c; vegetative insecticidal proteins (VIP), e.g. VIP1, VIP2, VIP3 or VIP3A; insecticidal proteins of bacteria colonizing nematodes, e.g. Photorhabdus spp. or Xenorhabdus spp.; toxins produced by animals, such as scorpion toxins, arachnid toxins, wasp toxins, or other insect-specific neurotoxins; toxins produced by fungi, such Streptomycetes toxins, plant lectins, such as pea or barley lectins; agglutinins; proteinase inhibitors, such as trypsin inhibitors, serine protease inhibitors, patatin, cystatin or papain inhibitors; ribosome-inactivating proteins (RIP), such as ricin, maize-RIP, abrin, luffin, saporin or bryodin; steroid metabolism enzymes, such as 3-hydroxy-steroid oxidase, ecdysteroid-IDP-glycosyl-transferase, cholesterol oxidases, ecdysone inhibitors or HMG-CoA-reductase; ion channel blockers, such as blockers of sodium or calcium channels; juvenile hormone esterase; diuretic hormone receptors (helicokinin receptors); stilben synthase, bibenzyl synthase, chitinases or glucanases. In the context of the present invention these insecticidal proteins or toxins are to be under-stood expressly also as pre-toxins, hybrid proteins, truncated or otherwise modified proteins. Hybrid proteins are characterized by a new combination of protein domains, (see, e.g. WO 02/015701). Further examples of such toxins or genetically modified plants capable of synthesizing such toxins are dis-closed, e.g., in EP-A 374 753, WO 93/007278, WO 95/34656, EP-A 427 529, EP-A 451 878, WO 03/18810 and WO 03/52073. The methods for producing such genetically modified plants are generally known to the person skilled in the art and are described, e.g. in the publications mentioned above. These insecticidal proteins contained in the genetically modified plants impart to the plants producing these proteins tolerance to harmful pests from all taxonomic groups of athropods, especially to beetles (Coeloptera), two-winged insects (Diptera), and moths (Lepidoptera) and to nematodes (Nematoda). Genetically modified plants capable to synthesize one or more insecticidal proteins are, e.g., described in the publications mentioned above, and some of which are commercially available such as YieldGard® (corn cultivars producing the Cry1Ab toxin), YieldGard® Plus (corn cultivars producing Cry1Ab and Cry3Bb1 toxins), Starlink® (corn cultivars producing the Cry9c toxin), Herculex® RW (corn cultivars producing Cry34Ab1, Cry35Ab1 and the enzyme Phosphinothricin-N-Acetyltransferase [PAT]); NuCOTN® 33B (cotton cultivars producing the Cry1Ac toxin), Bollgard® I (cotton cultivars producing the Cry1Ac toxin), Bollgard® II (cotton cultivars producing Cry1Ac and Cry2Ab2 toxins); VIPCOT® (cotton cultivars producing a VIP-toxin); NewLeaf® (potato cultivars producing the Cry3A toxin); BtXtra®, NatureGard®, KnockOut®, BiteGard®, Protecta®, Bt11 (e.g. Agrisure® CB) and Bt176 from Syngenta Seeds SAS, France, (corn cultivars producing the Cry1Ab toxin and PAT enyzme), MIR604 from Syngenta Seeds SAS, France (corn cultivars producing a modified version of the Cry3A toxin, c.f. WO 03/018810), MON 863 from Monsanto Europe S.A., Belgium (corn cultivars produ-cing the Cry3Bb1 toxin), IPC 531 from Monsanto Europe S.A., Belgium (cotton cultivars producing a modified version of the Cry1Ac toxin) and 1507 from Pioneer Overseas Corporation, Belgium (corn cultivars producing the Cry1F toxin and PAT enzyme).

Furthermore, plants are also covered that are by the use of recombinant DNA techniques capable to synthesize one or more proteins to in-crease the resistance or tolerance of those plants to bacterial, viral or fungal pathogens. Examples of such proteins are the so-called “pathogenesis-related proteins” (PR proteins, see, e.g. EP-A 392 225), plant disease resistance genes (e.g. potato culti-vars, which express resistance genes acting against Phytophthora infestans derived from the mexican wild potato Solanum bulbocastanum) or T4-lyso-zym (e.g. potato cultivars capable of synthesizing these proteins with increased resistance against bacteria such as Erwinia amylvora). The methods for producing such genetically modi-fied plants are generally known to the person skilled in the art and are described, e.g. in the publications mentioned above.

Furthermore, plants are also covered that are by the use of recombinant DNA techniques capable to synthesize one or more proteins to increase the productivity (e.g. bio mass production, grain yield, starch content, oil content or protein content), tolerance to drought, salinity or other growth-limiting environ-mental factors or tolerance to pests and fungal, bacterial or viral pathogens of those plants.

Furthermore, plants are also covered that contain by the use of recombinant DNA techniques a modified amount of substances of content or new substances of content, specifically to improve human or animal nutrition, e.g. oil crops that produce healthpromoting long-chain omega-3 fatty acids or unsaturated omega-9 fatty acids (e.g. Nexera® rape, DOW Agro Sciences, Canada).

Furthermore, plants are also covered that contain by the use of recombinant DNA techniques a modified amount of substances of content or new substances of content, specifically to improve raw material production, e.g. potatoes that produce increased amounts of amylopectin (e.g. Amflora® potato, BASF SE, Germany).

Furthermore, it has been found that the isoxazolo[5,4-b]pyridines of the formula I are also suitable for the defoliation and/or desiccation of plant parts, for which crop plants such as cotton, potato, oilseed rape, sunflower, soybean or field beans, in particular cotton, are suitable. In this regard, compositions for the desiccation and/or defoliation of plants, processes for preparing these compositions and methods for desiccating and/or defoliating plants using the isoxazolo[5,4-b]pyridines of formula I have been found.

As desiccants, the isoxazolo[5,4-b]pyridines of formula I are particularly suitable for desiccating the above-ground parts of crop plants such as potato, oilseed rape, sunflower and soybean, but also cereals. This makes possible the fully mechanical harvesting of these important crop plants.

Also of economic interest is to facilitate harvesting, which is made possible by concentrating within a certain period of time the dehiscence, or reduction of adhesion to the tree, in citrus fruit, olives and other species and varieties of pernicious fruit, stone fruit and nuts. The same mechanism, i.e. the promotion of the development of abscission tissue between fruit part or leaf part and shoot part of the plants is also essential for the controlled defoliation of useful plants, in particular cotton.

Moreover, a shortening of the time interval in which the individual cotton plants mature leads to an increased fiber quality after harvesting.

The isoxazolo[5,4-b]pyridines of formula I, or the herbicidal compositions comprising the isoxazolo[5,4-b]pyridines of formula I, can be used, for example, in the form of ready-to-spray aqueous solutions, powders, suspensions, also highly concentrated aqueous, oily or other suspensions or dispersions, emulsions, oil dispersions, pastes, dusts, materials for broadcasting, or granules, by means of spraying, atomizing, dusting, spreading, watering or treatment of the seed or mixing with the seed. The use forms depend on the intended purpose; in any case, they should ensure the finest possible distribution of the active ingredients according to the invention.

The herbicidal compositions comprise an herbicidal effective amount of at least one isoxazolo[5,4-b]pyridines of formula I and auxiliaries which are customary for the formulation of crop protection agents.

Examples of auxiliaries customary for the formulation of crop protection agents are inert auxiliaries, solid carriers, surfactants (such as dispersants, protective colloids, emulsifiers, wetting agents and tackifiers), organic and inorganic thickeners, bactericides, antifreeze agents, antifoams, optionally colorants and, for seed formulations, adhesives.

The person skilled in the art is sufficiently familiar with the recipes for such formulations.

Examples of thickeners (i.e. compounds which impart to the formulation modified flow properties, i.e. high viscosity in the state of rest and low viscosity in motion) are polysaccharides, such as xanthan gum (Kelzan® from Kelco), Rhodopol®23 (Rhone Poulenc) or Veegum® (from R.T. Vanderbilt), and also organic and inorganic sheet minerals, such as Attaclay® (from Engelhardt).

Examples of antifoams are silicone emulsions (such as, for example, Silikon SRE, Wacker or Rhodorsil® from Rhodia), long-chain alcohols, fatty acids, salts of fatty acids, organofluorine compounds and mixtures thereof.

Bactericides can be added for stabilizing the aqueous herbicidal formulations. Examples of bactericides are bactericides based on diclorophen and benzyl alcohol hemiformal (Proxel® from ICI or Acticide® RS from Thor Chemie and Kathon® MK from Rohm & Haas), and also isothiazolinone derivates, such as alkylisothiazolinones and benzisothiazolinones (Acticide MBS from Thor Chemie).

Examples of antifreeze agents are ethylene glycol, propylene glycol, urea or glycerol.

Examples of colorants are both sparingly water-soluble pigments and water-soluble dyes. Examples which may be mentioned are the dyes known under the names Rhodamin B, C.I. Pigment Red 112 and C.I. Solvent Red 1, and also pigment blue 15:4, pigment blue 15:3, pigment blue 15:2, pigment blue 15:1, pigment blue 80, pigment yellow 1, pigment yellow 13, pigment red 112, pigment red 48:2, pigment red 48:1, pigment red 57:1, pigment red 53:1, pigment orange 43, pigment orange 34, pigment orange 5, pigment green 36, pigment green 7, pigment white 6, pigment brown 25, basic violet 10, basic violet 49, acid red 51, acid red 52, acid red 14, acid blue 9, acid yellow 23, basic red 10, basic red 108.

Examples of adhesives are polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol and tylose.

Suitable inert auxiliaries are, for example, the following:

mineral oil fractions of medium to high boiling point, such as kerosene and diesel oil, furthermore coal tar oils and oils of vegetable or animal origin, aliphatic, cyclic and aromatic hydrocarbons, for example paraffin, tetrahydronaphthalene, alkylated naphthalenes and their derivatives, alkylated benzenes and their derivatives, alcohols such as methanol, ethanol, propanol, butanol and cyclohexanol, ketones such as cyclohexanone or strongly polar solvents, for example amines such as N-methylpyrrolidone, and water.

Suitable carriers include liquid and solid carriers.

Liquid carriers include e.g. non-aqeuos solvents such as cyclic and aromatic hydrocarbons, e.g. paraffins, tetrahydronaphthalene, alkylated naphthalenes and their derivatives, alkylated benzenes and their derivatives, alcohols such as methanol, ethanol, propanol, butanol and cyclohexanol, ketones such as cyclohexanone, strongly polar solvents, e.g. amines such as N-methylpyrrolidone, and water as well as mixtures thereof.

Solid carriers include e.g. mineral earths such as silicas, silica gels, silicates, talc, kaolin, limestone, lime, chalk, bole, loess, clay, dolomite, diatomaceous earth, calcium sulfate, magnesium sulfate and magnesium oxide, ground synthetic materials, fertilizers such as ammonium sulfate, ammonium phosphate, ammonium nitrate and ureas, and products of vegetable origin, such as cereal meal, tree bark meal, wood meal and nutshell meal, cellulose powders, or other solid carriers.

Suitable surfactants (adjuvants, wetting agents, tackifiers, dispersants and also emulsifiers) are the alkali metal salts, alkaline earth metal salts and ammonium salts of aromatic sulfonic acids, for example lignosulfonic acids (e.g. Borrespers-types, Borregaard), phenolsulfonic acids, naphthalenesulfonic acids (Morwet types, Akzo Nobel) and dibutylnaphthalenesulfonic acid (Nekal types, BASF AG), and of fatty acids, alkyl- and alkylarylsulfonates, alkyl sulfates, lauryl ether sulfates and fatty alcohol sulfates, and salts of sulfated hexa-, hepta- and octadecanols, and also of fatty alcohol glycol ethers, condensates of sulfonated naphthalene and its derivatives with formaldehyde, condensates of naphthalene or of the naphthalenesulfonic acids with phenol and formaldehyde, polyoxyethylene octylphenol ether, ethoxylated isooctyl-, octyl- or nonylphenol, alkylphenyl or tributylphenyl polyglycol ether, alkylaryl polyether alcohols, isotridecyl alcohol, fatty alcohol/ethylene oxide condensates, ethoxylated castor oil, polyoxyethylene alkyl ethers or polyoxypropylene alkyl ethers, lauryl alcohol polyglycol ether acetate, sorbitol esters, lignosulfite waste liquors and proteins, denaturated proteins, polysaccharides (e.g. methylcellulose), hydrophobically modified starches, polyvinyl alcohol (Mowiol types Clariant), polycarboxylates (BASF AG, Sokalan types), polyalkoxylates, polyvinylamine (BASF AG, Lupamine types), polyethyleneimine (BASF AG, Lupasol types), polyvinylpyrrolidone and copolymers thereof.

Powders, materials for broadcasting and dusts can be prepared by mixing or concomitant grinding the active ingredients together with a solid carrier.

Granules, for example coated granules, impregnated granules and homogeneous granules, can be prepared by binding the active ingredients to solid carriers.

Aqueous use forms can be prepared from emulsion concentrates, suspensions, pastes, wettable powders or water-dispersible granules by adding water.

To prepare emulsions, pastes or oil dispersions, the isoxazolo[5,4-b]pyridines of formula I, either as such or dissolved in an oil or solvent, can be homogenized in water by means of a wetting agent, tackifier, dispersant or emulsifier. Alternatively, it is also possible to prepare concentrates comprising active compound, wetting agent, tackifier, dispersant or emulsifier and, if desired, solvent or oil, which are suitable for dilution with water.

The concentrations of the isoxazolo[5,4-b]pyridines of formula I in the ready-to-use preparations (formulations) can be varied within wide ranges. In general, the formulations comprise approximately from 0.001 to 98% by weight, preferably 0.01 to 95% by weight of at least one active ingredient. The active ingredients are employed in a purity of from 90% to 100%, preferably 95% to 100% (according to NMR spectrum).

In the formulation of the isoxazolo[5,4-b]pyridines of formula I according to the present invention the active ingredients, e.g. the isoxazolo[5,4-b]pyridines of formula I, are present in suspended, emulsified or dissolved form. The formulation according to the invention can be in the form of aqueous solutions, powders, suspensions, also highlyconcentrated aqueous, oily or other suspensions or dispersions, aqueous emulsions, aqueous microemulsions, aqueous suspo-emulsions, oil dispersions, pastes, dusts, materials for spreading or granules.

The isoxazolo[5,4-b]pyridines of formula I according to the present invention can, for example, be formulated as follows:

1. Products for Dilution with Water

A Water-Soluble Concentrates

10 parts by weight of active compound are dissolved in 90 parts by weight of water or a water-soluble solvent. As an alternative, wetters or other adjuvants are added. The active compound dissolves upon dilution with water. This gives a formulation with an active compound content of 10% by weight.

B Dispersible Concentrates

20 parts by weight of active compound are dissolved in 70 parts by weight of cyclohexanone with addition of 10 parts by weight of a dispersant, for example polyvinylpyrrolidone. Dilution with water gives a dispersion. The active compound content is 20% by weight.

C Emulsifiable Concentrates

15 parts by weight of active compound are dissolved in 75 parts by weight of an organic solvent (eg. alkylaromatics) with addition of calcium dodecylbenzenesulfonate and castor oil ethoxylate (in each case 5 parts by weight). Dilution with water gives an emulsion. The formulation has an active compound content of 15% by weight.

D Emulsions

25 parts by weight of active compound are dissolved in 35 parts by weight of an organic solvent (eg. alkylaromatics) with addition of calcium dodecylbenzenesulfonate and castor oil ethoxylate (in each case 5 parts by weight). This mixture is introduced into 30 parts by weight of water by means of an emulsifier (Ultraturrax) and made into a homogeneous emulsion. Dilution with water gives an emulsion. The formulation has an active compound content of 25% by weight.

E Suspensions

In an agitated ball mill, 20 parts by weight of active compound are comminuted with addition of 10 parts by weight of dispersants and wetters and 70 parts by weight of water or an organic solvent to give a fine active compound suspension. Dilution with water gives a stable suspension of the active compound. The active compound content in the formulation is 20% by weight.

F Water-Dispersible Granules and Water-Soluble Granules

50 parts by weight of active compound are ground finely with addition of 50 parts by weight of dispersants and wetters and made into water-dispersible or water-soluble granules by means of technical appliances (for example extrusion, spray tower, fluidized bed). Dilution with water gives a stable dispersion or solution of the active compound. The formulation has an active compound content of 50% by weight.

G Water-Dispersible Powders and Water-Soluble Powders

75 parts by weight of active compound are ground in a rotor-stator mill with addition of 25 parts by weight of dispersants, wetters and silica gel. Dilution with water gives a stable dispersion or solution of the active compound. The active compound content of the formulation is 75% by weight.

H Gel Formulations

In a ball mill, 20 parts by weight of active compound, 10 parts by weight of dispersant, 1 part by weight of gelling agent and 70 parts by weight of water or of an organic solvent are mixed to give a fine suspension. Dilution with water gives a stable suspension with active compound content of 20% by weight.

2. Products to be Applied Undiluted

I Dusts

5 parts by weight of active compound are ground finely and mixed intimately with 95 parts by weight of finely divided kaolin. This gives a dusting powder with an active compound content of 5% by weight.

J Granules (GR, FG, GG, MG)

0.5 parts by weight of active compound are ground finely and associated with 99.5 parts by weight of carriers. Current methods here are extrusion, spray-drying or the fluidized bed. This gives granules to be applied undiluted with an active compound content of 0.5% by weight.

K ULV Solutions (UL)

10 parts by weight of active compound are dissolved in 90 parts by weight of an organic solvent, for example xylene. This gives a product to be applied undiluted with an active compound content of 10% by weight.

Aqueous use forms can be prepared from emulsion concentrates, suspensions, pastes, wettable powders or water-dispersible granules by adding water.

The isoxazolo[5,4-b]pyridines of formula I or the herbicidal compositions comprising them can be applied pre-, post-emergence or pre-plant, or together with the seed of a crop plant. It is also possible to apply the herbicidal composition or active compounds by applying seed, pretreated with the herbicidal compositions or active compounds, of a crop plant. If the active ingredients are less well tolerated by certain crop plants, application techniques may be used in which the herbicidal compositions are sprayed, with the aid of the spraying equipment, in such a way that as far as possible they do not come into contact with the leaves of the sensitive crop plants, while the active ingredients reach the leaves of undesirable plants growing underneath, or the bare soil surface (post-directed, lay-by).

In a further embodiment, the isoxazolo[5,4-b]pyridines of formula I or the herbicidal compositions can be applied by treating seed. The treatment of seeds comprises essentially all procedures familiar to the person skilled in the art (seed dressing, seed coating, seed dusting, seed soaking, seed film coating, seed multilayer coating, seed encrusting, seed dripping and seed pelleting) based on the isoxazolo[5,4-b]pyridines of formula I according to the invention or the compositions prepared therefrom. Here, the herbicidal compositions can be applied diluted or undiluted.

The term “seed” comprises seed of all types, such as, for example, corns, seeds, fruits, tubers, seedlings and similar forms. Here, preferably, the term seed describes corns and seeds.

The seed used can be seed of the useful plants mentioned above, but also the seed of transgenic plants or plants obtained by customary breeding methods.

The rates of application of the active isoxazolo[5,4-b]pyridines of formula I according to the present invention (total amount of isoxazolo[5,4-b]pyridines of formula I) are from 0.1 g/ha to 3000 g/ha, preferably 10 g/ha to 1000 g/ha of active substance (a.s.), depending on the control target, the season, the target plants and the growth stage.

In another preferred embodiment of the invention, the application rates of the isoxazolo[5,4-b]pyridines of formula I are in the range from 0.1 g/ha to 5000 g/ha and preferably in the range from 1 g/ha to 2500 g/ha or from 5 g/ha to 2000 g/ha of active substance (a.s.).

In another preferred embodiment of the invention, the application rate of the isoxazolo[5,4-b]pyridines of formula I is 0.1 to 1000 g/ha, preferably 1 to 750 g/ha, more preferably 5 to 500 g/ha, of active substance.

To treat the seed, the isoxazolo[5,4-b]pyridines I are generally employed in amounts of from 0.001 to 10 kg per 100 kg of seed.

To widen the spectrum of action and to achieve synergistic effects, the isoxazolo[5,4-b]pyridines of the formula I may be mixed with a large number of representatives of other herbicidal or growth-regulating active ingredient groups and then applied concomitantly. Suitable components for mixtures are, for example, 1,2,4-thiadiazoles, 1,3,4-thiadiazoles, amides, aminophosphoric acid and its derivatives, aminotriazoles, anilides, (het)aryloxyalkanoic acids and their derivatives, benzoic acid and its derivatives, benzothiadiazinones, 2-aroyl-1,3-cyclohexanediones, 2-hetaroyl-1,3-cyclohexanediones, hetaryl aryl ketones, benzylisoxazolidinones, meta-CF₃-phenyl derivatives, carbamates, quinolinecarboxylic acid and its derivatives, chloroacetanilides, cyclohexenone oxime ether derivatives, diazines, dichloropropionic acid and its derivatives, dihydrobenzofurans, dihydrofuran-3-ones, dinitroanilines, dinitrophenols, diphenyl ethers, dipyridyls, halocarboxylic acids and their derivatives, ureas, 3-phenyluracils, imidazoles, imidazolinones, N-phenyl-3,4,5,6-tetrahydrophthalinnides, oxadiazoles, oxiranes, phenols, aryloxy- and hetaryloxyphenoxypropionic esters, phenylacetic acid and its derivatives, 2-phenylpropionic acid and its derivatives, pyrazoles, phenylpyrazoles, pyridazines, pyridinecarboxylic acid and its derivatives, pyrimidyl ethers, sulfonamides, sulfonylureas, triazines, triazinones, triazolinones, triazolecarboxamides, uracils, phenyl pyrazolines and isoxazolines and derivatives thereof.

It may furthermore be beneficial to apply the isoxazolo[5,4-b]pyridines of formula I alone or in combination with other herbicides, or else in the form of a mixture with other crop protection agents, for example together with agents for controlling pests or phytopathogenic fungi or bacteria. Also of interest is the miscibility with mineral salt solutions, which are employed for treating nutritional and trace element deficiencies. Other additives such as non-phytotoxic oils and oil concentrates may also be added.

Moreover, it may be useful to apply the isoxazolo[5,4-b]pyridines of formula I in combination with safeners. Safeners are chemical compounds which prevent or reduce damage on useful plants without having a major impact on the herbicidal action of the isoxazolo[5,4-b]pyridines of formula I towards unwanted plants. They can be applied either before sowings (e.g. on seed treatments, shoots or seedlings) or in the preemergence application or post-emergence application of the useful plant. The safeners and the isoxazolo[5,4-b]pyridines of formula I can be applied simultaneously or in succession.

Suitable safeners are, for example, (quinolin-8-oxy)acetic acids, 1-phenyl-5-haloalkyl-1H-1,2,4-triazole-3-carboxylic acids, 1-phenyl-4,5-dihydro-5-alkyl-1H-pyrazole-3,5-dicarboxylic acids, 4,5-dihydro-5,5-diary)-3-isoxazolecarboxylic acids, dichloroacetamides, alpha-oximinophenylacetonitriles, acetophenonoximes, 4,6-dihalo-2-phenylpyrimidines, N-[[4-(aminocarbonyl)phenyl]sulfonyl]-2-benzamides, 1,8-naphthalic anhydride, 2-halo-4-(haloalkyl)-5-thiazolecarboxylic acids, phosphorothioates, N-alkyl-O-phenylcarbannates and 2-oxo-nicotinamides and their agriculturally suitable salts, and, assuming that they have an acid function, their agriculturally suitable derivatives such as amides, esters and thioesters.

Hereinbelow, the preparation of representative isoxazolo[5,4-b]pyridines of formula I is illustrated by examples:

-   -   NMR spectra were recorded on a Bruker Avance II 300. LC-MS were         recorded on a Waters system with the following conditions:         Column: XTerra MS C₁₈ 5 μm (4.6×100 mm)         Gradient: from 95% H₂O/5% MeOH to 100% MeOH in 8 min         Flow: 1.5 mL/min

Alternatively, a Shimadzu Nexera UHPLC in combination with Shimadzu LCMS 20-20, ESI was used; column: Phenomenex Kinetex 1.7 μm XB-C18 100A;

Synthesis of Compound 1

Na (14.67 g, 0.64 mmol) was dissolved in dry MeOH (0.8 L) and a solution of cyclopropylmethylketone (50 g, 0.59 mmol) and dimethyloxalate (70.2 g, 0.59 mmol) in dry MeOH (0.2 L) was added dropwise at 0° C. The reaction mixture was stirred at r.t. 24 h and reflux overnight. Water (0.5 L) was added and the methanol was removed under reduced pressure. The aqueous solution was washed with Et₂O (150 mL), acidified to pH=2 with 2M H₂SO₄ and extracted with Et₂O (3×150 mL). The organic layer was dried over MgSO₄ and concentrated to dryness, to yield compound 1 (55.6 g, 55%), which was used without further purification.

¹H-NMR (CDCl₃): δ=14.61 (br, 1H), 6.84 (s, 1H), 3.90 (s, 3H), 1.95-1.82 (m, 1H), 1.26-1.20 (m, 2H), 1.10-1.00 (m, 2H).

Synthesis of Compound 2

A mixture of compound 1 (0.9 g, 5.3 mmol) and 5-amino-3-(2-phenylethyl)isoxazole (1.0 g, 5.3 mmol) in AcOH (16 mL) was stirred at reflux for 4 h. The reaction mixture was poured into ice/water (100 mL). The solid formed was collected by filtration and dried under high vacuum. 1.5 g (79%) of compound 2 were obtained.

¹H-NMR (CDCl₃): δ=7.62 (s, 1H), 7.27-7.11 (m, 5H), 3.93 (s, 3H), 3.43-3.37 (m, 2H) 3.03-2.97 (m, 2H), 2.22-2.10 (m, 1H), 1.24-1.17 (m, 2H), 1.13-1.05 (m, 2H).

MS: m/z=323 [M+H]+, 345 [M+Na]+

Synthesis of Compound 3

A solution of compound 2 (1.0 g, 3.1 mmol) in a mixture 1:1 THF/1N NaOH (15 mL) was stirred at r.t. for 2 h. The reaction was concentrated in vacuum, the aqueous solution was acidified to pH=2 with 10% HCl and extracted with AcOEt (3×10 mL). The organic layer was dried over MgSO₄ and concentrated to dryness. The residue was stirred in petroleum/Et₂O 10:1 and the solid obtained was collected by filtration and dried under high vacuum to yield compound 3 (0.82 g, 85%).

¹H-NMR (CDCl₃): δ=7.81 (s, 1H), 7.31-7.13 (m, 5H), 3.52-3.46 (m, 2H) 3.12-3.05 (m, 2H), 2.34-2.22 (m, 1H), 1.34-1.28 (m, 2H), 1.26-1.17 (m, 2H).

MS: m/z=331 [M+Na]+, 353 [M−H+2Na]+, 639 [2M−2H+3Na]+

Synthesis of Compound 4

A mixture of compound 1 (3 g, 17.6 mmol) and 5-amino-3-methylisoxazole (1.73 g, 17.6 mmol) in AcOH (44 mL) was stirred at reflux for 2 h. The reaction mixture was poured into ice/water (100 mL). The solid formed was collected by filtration and dried under high vacuum. 3.9 g (97%) of compound 4 were obtained.

¹H-NMR (CDCl₃): δ=7.69 (s, 1H), 4.02 (s, 3H), 2.69 (s, 3H), 2.26-2.15 (m, 1H), 1.28-1.21 (m, 2H), 1.19-1.11 (m, 2H).

MS: m/z=233 [M+H]+

Synthesis of Compound 5

A solution of compound 4 (2.7 g, 11.6 mmol) in a mixture 1:1 THF/1N NaOH (52 mL) was stirred at r.t. for 1.5 h. The reaction was concentrated in vacuum, the aqueous solution was acidified to pH=2 with 10% HCl and the solid formed was collected by filtration and dried under high vacuum to yield compound 5 (2.4 g, 94%).

¹H-NMR (DMSO-d₆): δ=7.78 (s, 1H), 2.59 (s, 3H), 2.46-2.36 (m, 1H), 1.18-1.01 (m, 4H).

MS: m/z=219 [M+H]+.

Synthesis of Compound 6

A mixture of compound 5 (0.7 g, 3.2 mmol) in SOCl₂ (6.4 mL) was refluxed overnight. The volatiles were removed under vacuum using toluene as co-solvent. 760 mg of compound 6 were obtained and used without further purification.

Synthesis of Compound 7

To a solution of compound 6 (0.38 g, 1.6 mmol) in dry dichloromethane (8 mL) were added methanosulfonamide (0.17 g, 1.8 mmol) and N,N-Diisopropylethylamine (0.25 g, 1.9 mmol) at 0° C. The mixture was stirred at r.t. for 12 h. The reaction mixture was poured into aq. 5% citric acid (20 mL) and extracted with dichloromethane (3×10 mL). The organic layer was dried over MgSO₄ and concentrated to dryness. The residue was stirred in Et₂O and the solid formed was collected by filtration and after drying it was purified by prep. TLC (SiO₂, CHCl₃/MeOH 95:5). 160 mg (34%) of compound 7 were obtained.

¹H-NMR (CDCl₃): δ=7.36 (s, 1H), 3.37 (s, 3H), 2.57 (s, 3H), 2.22-2.11 (m, 1H), 1.25-1.05 (m, 4H).

MS: m/z=347 [M+Na]+, 671 [2M+Na]+.

Synthesis of compound 8

To a solution of N-methoxy-N-methyl cyclopropanecarboxamide (8 g, 62 mmol) in dry THF (93 mL) was added dropwise at 78° C. a solution 1M ethylmagnesiumbromide in THF (62 mL, 62 mmol) under nitrogen atmosphere. The reaction mixture was slowly allowed to warm up to 0° C., poured into phosphate buffer solution (150 mL, pH=7) and extracted with Et₂O (3×50 mL). The organic layer was dried over MgSO₄ and concentrated at 45° C./400 mbar. The residue consisted in a mixture 1:2 compound 8/THF (9.2 g, ˜3.7 g product, ˜61%) and it was used without further purification.

¹H-NMR (CDCl₃): δ=2.54 (c, J=7.33 Hz, 2H), 1.94-1.84 (m, 1H), 1.04 (t, J=7.33 Hz, 3H), 1.00-0.92 (m, 2H), 0.85-0.76 (m, 2H).

Synthesis of Compound 9

Na (0.93 g, 40.4 mmol) was dissolved in dry MeOH (52 mL) and a solution of compound 8 (3.7 g, 37.7 mmol) and dimethyloxalate (4.45 g, 37.7 mol) in dry MeOH (15 mL) was added dropwise at 0° C. The reaction mixture was stirred at r.t. 18 h. Dimethyloxalate (4.45 g, 37.7 mol) and 30% NaOMe in MeOH (7.5 mL) were added and the mixture was stirred at r.t. 18 h. More 30% NaOMe in MeOH (2.5 mL) was added and the mixture was stirred at r.t. 18 h before it was poured into water (200 mL). The methanol was removed under reduced pressure. The aqueous solution was washed with Et₂O (25 mL), acidified to pH=2 with 2M H₂SO₄ and extracted with Et₂O (3×50 mL). The organic layer was dried over MgSO₄ and concentrated to dryness, to yield compound 9 (5.1 g, ˜82%) which was used without further purification.

Synthesis of Compound 10

A mixture of compound 9 (5 g, 27.1 mmol) and 5-amino-3-methylisoxazole (2.66 g, 27.1 mmol) in AcOH (78 mL) was stirred at reflux for 1 h. The reaction mixture was concentrated to dryness and the residue was dissolved in AcOEt (50 mL) and washed with aq. sat. NaHCO3 (2×15 mL). The organic layer was dried over MgSO₄ and concentrated to dryness. The residue was purified by flash column chromatography (SiO₂, c-Hex/AcOEt) to yield compound 10 (1.3 g, 18%).

¹H-NMR (CDCl₃): δ=2.50 (s, 3H), 2.43 (s, 3H), 2.30-2.20 (m, 1H), 1.30-1.22 (m, 2H), 1.16-1.07 (m, 2H).

MS: m/z=269 [M+Na]+.

Synthesis of Compound 11

A solution of compound 10 (0.6 g, 2.1 mmol) in a mixture 1:1 THF/1N NaOH (12 mL) was stirred at r.t. for 12 h. The reaction was concentrated in vacuum, the aqueous solution was acidified to pH=2 with 10% HCl and extracted with dichloromethane (3×25 mL). The organic layer was dried over MgSO₄ and concentrated to dryness. The residue was stirred in petroleum ether/Et₂O 10:1 and the solid obtained was collected by filtration and dried under high vacuum to yield compound 11 (0.41 g, 85%).

¹H-NMR (MeOD-d₄): δ=2.44 (s, 3H), 2.38 (s, 3H), 2.32-2.25 (m, 1H), 1.10-1.00 (m, 2H).

MS: m/z=233 [M+H]+, 255 [M+Na]+, 277 [M−H+2Na]+.

Synthesis of Compound 12

Na (0.76 g, 33.1 mmol) was dissolved in dry MeOH (42 mL) and a solution of 3,3,4,4,4-Pentafluoro-butan-2-one (5 g, 30.9 mmol) and dimethyloxalate (3.64 g, 30.9 mmol) in dry MeOH (13 mL) was added dropwise at 0° C. The reaction mixture was stirred at r.t. overnight. Water (50 mL) was added and the methanol was removed under reduced pressure. The aqueous solution was washed with Et₂O (25 mL), acidified to pH=2 with 2M H₂SO₄ and extracted with Et₂O (3×25 mL). The organic layer was dried over MgSO₄ and concentrated to dryness, to yield compound 12 (2 g, 26%) which was used without further purification.

¹H-NMR (CDCl₃): δ=6.28 (s, 1H), 3.92 (s, 3H).

Synthesis of Compound 13

A mixture of compound 12 (2 g, 8.1 mmol) and 5-amino-3-methylisoxazole (0.67 g, 6.8 mmol) in AcOH (20 mL) was stirred at reflux for 1 h. The reaction mixture was poured into ice/water (50 mL) and extracted with Et₂O (3×25 ml). The organic layer was washed with aq. sat. NaHCO3 (2×15 mL), dried over MgSO₄ and concentrated to dryness. The reaction crude was purified by flash column chromatography (SiO₂, c-Hex/AcOEt) to give 60 mg of compound 13 (2.4%).

Synthesis of Compound 14

A solution of compound 13 (56 mg, 0.2 mmol) in a mixture 1:1 THF/1N NaOH (2 mL) was stirred at r.t. for 4 h. The reaction was concentrated in vacuum, the aqueous solution was acidified to pH=2 with 10% HCl and extracted with dichloromethane (3×5 mL). The organic layer was dried over MgSO₄ and concentrated to dryness. The residue was stirred in petroleum ether/Et₂O 10:1 and the solid obtained was collected by filtration and dried under high vacuum to yield compound 14 (44 mg, 88%).

¹H-NMR (CDCl₃): δ=8.31 (s, 1H), 2.86 (s, 3H).

MS: m/z=319 [M+Na]+, 341 [M−H+2Na]+

Synthesis of Compound 16

A mixture of compound 15 (0.85 g, 3.9 mmol) and p-toluenesulfonic acid (0.27 g, 1.5 mmol) in MeOH (17 mL) was refluxed for 4 days. The solvent was removed and the residue was diluted with a mixture CHCl₃/2-propanol 7:3 (50 mL) and washed with aq. sat. NaHCO3 (2×15 mL). The organic layer was dried over MgSO₄ and concentrated to dryness. 620 mg (69%) of compound 16 were obtained and used without further purification.

¹H-NMR (CDCl₃): δ=7.19 (s, 1H), 4.04 (s, 3H), 2.59-2.44 (m, 1H), 1.25-1.17 (m, 2H), 1.15-1.00 (m, 2H).

MS: m/z=335 [M+H]+, 357 [M+Na]+

Synthesis of Compound 17

To a solution of compound 16 (0.19 g, 0.8 mmol) in dry dichloromethane (3 mL) were added at 0° C. pyridine (80 mg, 1 mmol) and trifluoromethanosulfonic anhydride (0.29 g, 1 mmol) and the mixture was stirred at this temperature for ½ h and at r.t. for 8 h. The reaction was diluted with water (3 mL) and extracted with DCM (2×5 mL). The organic layer was dried over MgSO₄ and concentrated to dryness. The reaction crude was purified by flash column chromatography to give 190 mg (63%) of compound 17.

¹H-NMR (CDCl₃): δ=7.66 (s, 1H), 4.07 (s, 3H), 2.71-2.57 (m, 1H), 1.22-1.10 (m, 4H).

MS: m/z=367 [M+H]+.

Synthesis of Compound 18

A mixture of compound 17 (150 mg, 0.41 mmol), LiCl (90 mg, 2.1 mmol), tributylvinyltin (170 mg, 0.53 mmol) and bis(triphenylphosphine)palladium (II) dichloride (50 mg, 0.07 mmol) in dry DMF (5 mL) was stirred at 80° C. for 1 h. After cooling down, a solution of NaF (390 mg) in water (4.5 mL) was added and the mixture was stirred at r.t. for 1 h. The reaction mixture was filtered through a celite-pad and the filter-cake was washed with AcOEt. The layers of the filtrate were separated, the aqueous layer was extracted with AcOEt (3×10 mL) and the combined organic layer was dried over MgSO₄ and concentrated to dryness. The reaction crude was purified by flash column chromatography to give 80 mg (80%) of compound 18. The compound so obtained presented some impurities from tin-reagent.

¹H-NMR (CDCl₃): δ=7.81 (s, 1H), 6.92 (dd, J=17.4, 10.7 Hz, 1H), 6.51 (d, J=17.4 Hz, 1H), 5.73 (d, J=10.7 Hz, 1H), 4.04 (s, 3H), 2.67-2.57 (m, 1H), 1.20-1.14 (m, 2H), 1.13-1.05 (m, 2H).

MS: m/z=467 [M+Na]+.

Synthesis of Compound 19

To a solution of compound 18 (100 mg, 0.41 mmol) in dichloromethane (4 mL) was added at 0° C. a solution of meta-chloroperoxybenzoic acid (71 mg, 0.41 mmol) in dichloromethane (4 mL), which was previously dried over MgSO₄. The reaction mixture was stirred at r.t 24 h, before a new solution of meta-chloroperoxybenzoic acid (71 mg, 0.41 mmol) in dichloromethane (4 mL) was added. This operation was repeated twice. The mixture was washed with aq. sat. NaHCO3 (3×10 mL) and the organic layer was dried over MgSO₄ and concentrated to dryness. The residue was purified by prep. TLC (SiO₂, c-Hex/AcOEt), to give 45 mg (41%) of compound 19. The compound 19 so obtained contained some meta-chlorobenzoic acid.

¹H-NMR (CDCl₃): δ=7.69 (s, 1H), 4.19-4.14 (m, 1H), 4.03 (s, 3H), 3.29 (dd, J=5.1, 4.1 Hz, 1H), 3.01 (dd, J=5.3, 2.1 Hz, 1H), 2.70-2.57 (m, 1H), 1.20-1.14 (m, 2H), 1.14-1.07 (m, 2H).

Synthesis of Compound 20

A mixture of compound 1 (17 g, 0.1 mol) and 5-amino-isoxazol-3-one (10 g, 0.1 mol) in acetic acid (AcOH) (100 mL) was stirred at reflux for 2 h. The reaction mixture was poured into ice/water (200 mL). The solid formed was collected by filtration and dried under high vacuum. 19 g (82%) of compound 20 were obtained.

¹H-NMR (CDCl₃): δ=10.30 (bs, 1H), 7.69 (s, 1H), 4.12 (s, 3H), 2.27-2.20 (m, 1H), 1.29-1.22 (m, 2H), 1.21-1.12 (m, 2H).

MS: m/z=235 [M+H]+

Synthesis of Compound 21

To a stirred solution of triphenylphosphine (12.3 g, 46.9 mmol) in dry THF (150 mL) was added dropwise diisopropyl azodicarboxylate (9.5 g, 46.9 mmol) at 0° C. under nitrogen atmosphere, and the mixture was stirred for 20 min. Then, t-BuOH (3.5 g, 47.2 mmol) and compound 20 (10 g, 42.7 mmol) were added at 0° C. The mixture was stirred at r.t. for 2 h and heated to 40° C., stirred overnight. The mixture was cooled to r.t and another portion of triphenylphosphine (12.3 g, 46.9 mmol), t-BuOH (3.5 g, 47.2 mmol) and diisopropyl azodicarboxylate (9.5 g, 46.9 mmol) were added. The mixture was stirred at r.t. for 1 h and heated to 60° C., stirred overnight. The solvent was removed under reduced pressure. The residue was purified by column chromatography (SiO₂, c-Hex/AcOEt) to give compound 21 (5.6 g, yield: 45%)

¹H-NMR (CDCl₃): δ=7.52 (s, 1H), 4.00 (s, 3H), 2.25-2.16 (m, 1H), 1.65 (s, 9H), 1.28-1.21 (m, 2H), 1.19-1.11 (m, 2H).

MS: m/z=235 [M−tBu+H]+

Synthesis of Compound 22

A mixture of compound 20 (12 g, 0.05 mmol), pyridine hydrochloride (20 g, 0.17 mol), H₃PO₄ (3.6 g, 0.04 mmol) and POCl₃ (120 mL) was stirred at 90° C. for 3 h. The excess of POCl₃ was evaporated under high vacuum. Remaining mixture was dissolved in ethyl acetate and slowly neutralized with NaHCO3 at 0° C. The organic layer was washed with brine and water, dried over MgSO₄ and concentrated to dryness. The residue was purified by column chromatography (SiO₂, c-Hex/AcOEt) to give compound 22 (6.5 g, yield: 50%).

¹H-NMR (CDCl₃): δ=7.72 (s, 1H), 4.05 (s, 3H), 2.29-2.20 (m, 1H), 1.32-1.26 (m, 2H), 1.25-1.18 (m, 2H).

MS: m/z=253 [M+H]+

Synthesis of Compound 24

To the solution of hydroxy-acetic acid ethyl ester 23 (99.6 g, 0.96 mmol) in THF (1.5 L) under nitrogen atmosphere, NaH (42 g, 1.0 mol: 60% in mineral oil) was added at 0° C. in portions. The mixture was stirred at 0° C. for 30 min and tetrabutylammonium iodide (35.3 g, 0.10 mol) and benzyl bromide (163.6 g, 0.96 mmol) were added. The mixture was allowed to warm up to r.t and was stirred in this temperature for 12 h. The reaction mixture was diluted with water and extracted with ethyl acetate. The organic layer was dried over MgSO₄, solvent was evaporated under high vacuum and raw product was destilled (121° C./4 mBar) to give compound 24 (135.5 g, yield: 73%).

¹H-NMR (CDCl₃): δ=7.41-7.22 (m, 5H), 4.65 (s, 2H), 4.27 (q, 2H), 4.11 (s, 2H), 1.25 (t, 3H).

Synthesis of Compound 25

Tetrahydrofuran (1 L) and NaH (30 g, 0.77 mol: 60% in mineral oil) were stirred under nitrogen atmosphere and heated to 50° C. To this mixture, a tertahydrofuran solution of compound 24 (135.5 g, 0.70 mol) and acetonitrile (37.1 g, 0.90 mol) were added. The reaction was stirred at r.t. for 12 h. The reaction mixture was diluted with water and extracted with MTBE (Methyl tert-butyl ether). The water phase was acidified with citric acid (pH=3) and extracted with ethyl acetate. The organic layer was washed with brine and water, dried over MgSO₄ and concentrated to dryness. The residue was purified by column chromatography (SiO₂, c-Hex/AcOEt) to give compound 25 (41 g, yield: 31%)

¹H-NMR (CDCl₃): δ=7.40-7.21 (m, 5H), 4.58 (s, 2H), 4.10 (s, 2H), 3.61 (s, 2H).

Synthesis of Compound 26

A mixture of compound 25 (63.3 g, 0.33 mmol), hydroxylamine hydrochloride (30.2 g, 0.43 mmol) and sodium acetate (82.3 g, 1 mol) in EtOH (1 L) was stirred at r.t. for 4 h. Solvent was removed under high vacuum. The reaction mixture was poured into water and extracted with methylene chloride. The organic layer was washed with brine and water, dried over MgSO₄ and concentrated to dryness. The residue was purified by column chromatography (SiO₂, c-Hex/AcOEt) to give compound 26 (13.8 g, yield: 20%).

¹H-NMR (CDCl₃): δ=7.40-7.22 (m, 5H), 5.20 (s, 1H), 4.55 (bs, 4H), 4.46 (s, 2H).

Synthesis of Compound 27

A mixture of compound 1 (11.5 g, 0.07 mol) and 26 (13.8 g, 0.07 mol) in AcOH (150 mL) was stirred at reflux for 2 h. The reaction mixture was poured into ice/water (200 mL). The solid formed was collected by filtration and dried under high vacuum. 16.5 g (72%) of compound 27 were obtained.

¹H-NMR (CDCl₃): δ=7.68 (s, 1H), 7.32 (s, 5H), 5.03 (s, 2H), 4.60 (s, 2H), 3.95 (s, 3H), 2.26-2.20 (m, 1H), 1.30-1.25 (m, 2H), 1.20-1.12 (m, 2H).

MS: m/z=339 [M+H]+

Synthesis of Compound 28

BCl₃ (5.9 mL, 5.91 mmol; 1M in CH₂Cl₂) was slowly added to a solution of compound 27 (1 g, 2.96 mmol) in CH₂Cl₂ (20 mL) at −78° C. and the reaction mixture was stirred at this temperature for 2 h. Saturated aqueous NaHCO3 was added. The layers were separated and the organic layer was washed with brine and water, dried over MgSO₄ and concentrated to dryness. The residue was stirred with diisopropylether and the solid formed was collected by filtration and dried under high vacuum to give compound 29 (0.5 g, yield: 68%).

¹H-NMR (CDCl₃): δ=7.80 (s, 1H), 5.00 (s, 2H), 4.07 (s, 3H), 3.88 (bs, 1H), 2.28-2.20 (m, 1H), 1.30-1.25 (m, 2H), 1.20-1.15 (m, 2H).

The isoxazolo[5,4-b]pyridines according to tables 7 to 14 below were prepared in accordance with the methods described above; compounds labeled “(−)” are not part of the present invention:

TABLE 7 compounds labeled “(-)” are not part of the present invention (I.1)

cpd.-no X R.T. (min) m/z = [M + H]+ I.1.1 (-)

3.241 370.1 I.1.2 (-)

3.082 401.1 I.1.3

2.781 345.1 I.1.4 (-)

3.527 385.1 I.1.5

3.541 477.1 I.1.6 OCH₂CN 3.147 258.1 I.1.7

3.734 426.2 I.1.8 (-)

2.892 409.1 I.1.9 (-)

3.943 383.1 I.1.10

3.943 383.1 I.1.11

4.283 361.1 I.1.12 (-)

3.741 406.2 I.1.13 (-)

3.646 384.1 I.1.14

4.106 353.1 I.1.15

3.899 366.1 I.1.16 (-)

3.473 410.1 I.1.17

3.941 381.1 I.1.18 (-)

3.490 324.1 I.1.19 (-)

3.604 366.1 I.1.20

3.477 483.1 I.1.21 (-)

3.794 350.1 I.1.22 (-)

3.530 380.1 I.1.23 (-)

3.491 422.2 I.1.24

2.600 290.1 I.1.25 (-)

3.847 386.2 I.1.26 (-)

3.346 391.1 I.1.27 (-)

3.927 437.1 I.1.28 (-)

2.883 422.1 I.1.29 (-)

2.978 330.1 I.1.30 (-)

4.140 395.1 I.1.31 (-)

4.043 406.1 I.1.32 (-)

4.057 434.2 I.1.33 (-)

3.875 436.2 I.1.34

3.686 344.1 I.1.35

3.804 372.2 I.1.36

4.082 388.2 I.1.37

4.156 417.1 I.1.38 (-)

3.503 386.1 I.1.39 OCH₃ 3.254 233.1 I.1.40

4.099 398.0 I.1.41 (-)

3.984 406.2 I.1.42 (-)

3.437 386.1 I.1.43 (CH₃)₃COCOCH₂O 3.989 333.1 I.1.44 (-)

3.624 396.1 I.1.45 (-)

3.778 424.2 I.1.46 (-)

3.813 414.1 I.1.47 (-)

4.073 405.1 I.1.48 (-)

3.636 358.2 I.1.49

4.063 371.1 I.1.50 (-)

3.653 412.2 I.1.51

3.767 357.1 I.1.52 (-)

3.990 386.2 I.1.53 OCH₂CO₂CH₃ 3.275 291.1 I.1.54 (-)

3.048 384.2 I.1.55 (-)

3.740 373.1 I.1.56

4.007 369.1 I.1.57 (-)

4.196 401.0 I.1.58 (-)

3.641 398.1 I.1.59

4.288 361.1 I.1.60

3.909 391.1 I.1.61 OCH₂OCH₃ 2.592 219.1 I.1.62 OCH₂CH═CH₂ 3.750 259.1 I.1.63 OCH₂CH₃ 3.609 247.1 I.1.64 OCH₂CH═CClCH₃ (Z-isomer) 4.170 219.1 I.1.65 OCH₂CHF₂ 3.539 283.1 I.1.66 OCH₂CH═C(CH₃)₂ 4.234 219.1 I.1.67 OCH₂CF₃ 3.824 301.1 I.1.68 OCH₂CCCH₃ 3.761 271.1 I.1.69 O(CH₂)₂OCH₂CH₃ 3.579 291.1 I.1.70 O[(CH₂)₂O]₂C₄H₉ 4.082 363.2 I.1.71 OC(CH₃)₂ 4.148 219.1 I.1.72 OC₃H₇ 3.936 261.1 I.1.73 OCH₂C(CH₃)₂ 4.431 289.1 I.1.74 O(CH₂)₂OH 2.641 263.1 I.1.75 O(CH₂)₂OCH═CH₂ 3.705 289.1 I.1.76 OCH₂CH═CHC≡CH 3.799 283.1 I.1.77 NHSO₂CH₃ 0.909 296   I.1.78 NHSO₂C₆H₅ 1.102 358   I.1.79 SCH₂C₆H₅ 1.441 325   I.1.80 SCH₂CHCH₂ 1.351 275   I.1.81 S(CH₂)₃CH₃ 1.480 291   I.1.82 SCH₃ 1.236 249   I.1.83 N(OCH₃)CH₃ 0.985 262  

TABLE 8 (I.2)

R.T. m/z = cpd.-no R³ (min) [M + H]+ I.2.1 CH₃ 2.574 219.1 I.2.2 CH₂C(CH₃)₂ 3.429 275.1 I.2.3 (CH₂)₂CH₃ 3.078 247.1 I.2.4

2.885 271.0 I.2.5 C₆H₅ 3.108 281.1 I.2.6 CH(CH₃)₂ 3.048 247.1 I.2.7

2.920 245.1 I.2.8 4-CH₃O—C₆H₄ 3.176 311.1 I.2.9

2.651 313.1 I.2.10 CF₃ 3.176 273.0 I.2.11 (CH₂)₂C₆H₅ 3.543 309.1 I.2.12

3.180 259.1 I.2.13

3.156 259.1 I.2.14

3.370 273.1 I.2.15

2.078 282.1 I.2.16

0.763 282   I.2.17 4-Cl—C₆H₄ 1.175 315   I.2.18 4-CF₃—C₆H₄ 1.234 349   I.2.19 4-C₆H₅—C₆H₄ 1.287 357   I.2.20 4-Br—C₆H₄ 1.194 360   I.2.21 3-CF₃—C₆H₄ 1.228 349   I.2.22 3-OCH₃—C₆H₄ 1.110 311   I.2.23 3-OCH₃,4-OCH₃—C₆H₃ 1.066 341   I.2.24 3-Cl—C₆H₄ 1.183 315   I.2.25 CH₂CH₃ 1.012 233   I.2.26

1.218 287   I.2.27

1.232 287   I.2.28 (CH₂)₄CH₃ 1.225 275   I.2.29

1.280 301   I.2.30

1.363 315   I.2.31 3-F—C₆H₄ 1.131 299   I.2.32 3-Cl,5-Cl—C₆H₃ 1.281 349 [M]+ I.2.33 2-OCH₃—C₆H₄ 1.090 311   I.2.34 2-OCH₃,3-OCH₃, 4-OCH₃—C₆H₂ 1.107 371   I.2.35 2-Cl—C₆H₄ 1.144 315   I.2.36 3-OCH₃,5-OCH₃—C₆H₃ 1.133 341   I.2.37 (CH₂)₃C₆H₄ 1.256 323   I.2.38 CH₂OCH₃ 0.938 249   I.2.39 (CH₂)₂CH(CH₃)₂ 1.218 275   I.2.40

1.238 329   I.2.41

1.304 313   I.2.42 (CH₂)₂-4-OCH₃—C₆H₄ 1.209 339   I.2.43 4-I—C₆H₄ 1.230 406 [M]+ I.2.44 3-F,5-F—C₆H₃ 1.178 317   I.2.45 4-OCHF₂—C₆H₄ 1.170 347   I.2.46

1.058 263   I.2.47

1.146 299   I.2.48 H 0.558 205   I.2.49 CH₂OH 0.825 235   I.2.50 2-F—C₆H₄ 1.126 299   I.2.51 4-F—C₆H₄ 1.123 299   I.2.52 2-CH₃—C₆H₄ 1.145 295   I.2.53 OCH₃ 0.933 235   I.2.54 OCH₂CH₃ 1.004 249   I.2.55 O(CH₂)₂CH₃ 1.084 263   I.2.56 O(CH₂)₃CH₃ 1.157 277   I.2.57 OCH(CH₃)₂ 1.075 263   I.2.58 OC(CH₃)₃ 1.142 277   I.2.59 2-Br—C₆H₄ 1.173 360   I.2.60 2-CF₃—C₆H₄ 1.245 349   I.2.61 4-CH₂CH₃—C₆H₄ 1.232 309   I.2.62 4-OCH₂CH₃—C₆H₄ 1.187 325   I.2.63 4-O(CH₂)₃CH₃—C₆H₄ 1.313 353   I.2.64 2-OCHF₂—C₆H₄ 1.152 347   I.2.65 4-NO₂—C₆H₄ 1.164 326   I.2.66 4-CH(CH₃)₂—C₆H₄ 1.279 323   I.2.67

1.107 285   I.2.68

1.125 285   I.2.69

1.148 301   I.2.70

1.168 301   I.2.71 4-C(CH₃)₃—C₆H₄ 1.333 337   I.2.72 OH 0.884 221   I.2.73

1.103 366   I.2.74 OCH(CH₂CH₃)₂ 1.237 291  

TABLE 9 (I.3)

R.T. m/z = cpd.-no R¹ X (min) [M + H]+ I.3.1 CH₂C₆H₅ OH 3.353 309.1 I.3.2 CH₃ OH 2.539 233.1 I.3.3 Br OH 2.606 297.0 I.3.4 Cl OH 2.568 253.0 I.3.5 CH₂C₆H₅ OC(CH₃)₃ 4.538 365.2 I.3.6 CH₃ OCH₃ 3.380 247.1 I.3.7 Br OCH₃ 3.770 311.0 I.3.8 Cl OCH₃ 3.732 267.0

TABLE 10 (I.4)

m/z = cpd.- R.T. [M + no R³ X (min) H]+ I.4.1

OCH₃ 4.134 287.1 I.4.2

OCH₃ 2.393 296.1 I.4.3

OCH₃ 3.897 273.1 I.4.4

OCH₃ 3.942 273.1 I.4.5 (CH₂)₂C₆H₅ OCH₃ 4.164 323.1 I.4.6 CF₃ OCH₃ 3.821 287.0 I.4.7 4-CH₃O—C₆H₄ OCH₃ 3.820 325.1 I.4.8 4-CH₃—C₆H₄ OCH₃ 4.055 309.1 I.4.9 4-F—C₆H₄ OCH₃ 3.882 313.1 I.4.10

OCH₃ 3.287 327.1 I.4.11 2-F—C₆H₄ OCH₃ 3.880 313.1 I.4.12

OCH₃ 3.085 327.1 I.4.13

OCH₃ 0.880 296   I.4.14 4-Cl—C₆H₄ OCH₃ 1.363 329   I.4.15 4-CF₃—C₆H₄ OCH₃ 1.390 363   I.4.16 4-C₆H₅—C₆H₄ OCH₃ 1.455 371   I.4.17 4-Br—C₆H₄ OCH₃ 1.377 374   I.4.18 3-CF₃—C₆H₄ OCH₃ 1.390 363   I.4.19 3-OCH₃—C₆H₄ OCH₃ 1.288 325   I.4.20 3-OCH₃,4-OCH₃—C₆H₃ OCH₃ 1.221 355   I.4.21 3-Cl—C₆H₄ OCH₃ 1.371 329   I.4.22 CH₂CH₃ OCH₃ 1.214 247   I.4.23

OCH₃ 1.443 301   I.4.24

OCH₃ 1.442 301   I.4.25 (CH₂)₄CH₃ OCH₃ 1.441 289   I.4.26

OCH₃ 1.502 315   I.4.27

OCH₃ 1.567 329   I.4.28 3-F—C₆H₄ OCH₃ 1.306 313   I.4.29 3-Cl,5-Cl—C₆H₃ OCH₃ 1.466 363   I.4.30 2-OCH₃—C₆H₄ OCH₃ 1.281 325   I.4.31 2-OCH₃,3-OCH₃, OCH₃ 1.276 385   4-OCH₃—C₆H₂ I.4.32 2-Cl—C₆H₄ OCH₃ 1.331 329   I.4.33 3-OCH₃,5-OCH₃—C₆H₃ OCH₃ 1.305 355   I.4.34 (CH₂)₃C₆H₄ OCH₃ 1.440 337   I.4.35 CH₂OCH₃ OCH₃ 1.115 263   I.4.36 (CH₂)₂CH(CH₃)₂ OCH₃ 1.437 289   I.4.37

OCH₃ 1.416 343   I.4.38

OCH₃ 1.517 327   I.4.39 (CH₂)₂-4-OCH₃—C₆H₄ OCH₃ 1.380 353   I.4.40 4-I—C₆H₄ OCH₃ 1.412 421   I.4.41 3-F,5-F—C₆H₃ OCH₃ 1.178 317   I.4.42 4-OCHF₂—C₆H₄ OCH₃ 1.327 361   I.4.43

OCH₃ 1.247 277   I.4.44

OCH₃ 1.319 313   I.4.45 CH₂C(CH₃)₃ SCH₃ 1.487 305   I.4.46 2-F—C₆H₄ SCH₃ 1.369 329   I.4.47 4-F—C₆H₄ SCH₃ 1.375 329   I.4.48 2-CH₃—C₆H₄ SCH₃ 1.398 325   I.4.49 OC(CH₃)₃ NH₂ 1.175 276   I.4.50 OC(CH₃)₃ SCH₃ 1.320 307   I.4.51 OCH(CH₃)₂ NH₂ 1.065 262   I.4.52 OCH(CH₃)₂ SCH₃ 1.378 293   I.4.53 OCH(CH₃)₂ SCH₂C₆H₅ 1.533 369   I.4.54 4-OCH₂CH₃—C₆H₄ SCH₃ 1.421 355   I.4.55 4-O(CH₂)₃CH₃—C₆H₄ SCH₃ 1.538 383   I.4.56 2-OCHF₂—C₆H₄ SCH₃ 1.362 377   I.4.57 4-NO₂—C₆H₄ SCH₃ 1.365 356   I.4.58 NHCH(CH₃)₂ CONHCH(CH₃)₂ 1.258 303   I.4.59 (CH₂)₂CH₃ SCH₃ 1.390 277   I.4.60

SCH₃ 1.338 275   I.4.61 2-Br—C₆H₄ SCH₃ 1.416 390   I.4.62 2-CF₃—C₆H₄ SCH₃ 1.463 379   I.4.63

NH₂ 0.918 244   I.4.64 OCOC(CH₃)₃ OCH₃ 1.402 319  

TABLE 11 compounds labeled “(−)” are not part of the present invention (I.5)

R.T. m/z = cpd.-no R² (min) [M + H]+ I.5.1 (−) 2-CF₃—C₆H₄ 3.539 323.0 I.5.2 CH₃ 1.941 193.0 I.5.3 CH(CH₃)₂ 2.693 221.1 I.5.4 CH₂CH₃ 2.330 207.1 I.5.5 (−) 2-F—C₆H₄ 3.052 273.0 I.5.6 (−) 4-F—C₆H₄ 3.167 273.0 I.5.7

2.610 244.0 I.5.8 (−) 2-CH₃—C₆H₄ 3.314 269.1 I.5.9

3.186 258.0 I.5.10

3.280 272.1 I.5.11 (−) 4-CH₃O—C₆H₄ 3.065 285.1 I.5.12

1.575 256.1 I.5.13 (−) 4-CHF₂O—C₆H₄ 3.306 321.0 I.5.14

2.545 273.1 I.5.15

3.005 233.1 I.5.16 (−) 4-NO₂—C₆H₄ 3.125 300.1 I.5.17 (−)

3.015 299.0 I.5.18 CH₂CH(CH₃)₂ 2.960 235.1 I.5.19 (CH₂)₄CH₃ 3.347 249.1 I.5.20

2.867 233.0 I.5.21

3.387 261.1 I.5.22

3.142 247.1 I.5.23 CH₂C₆H₅ 3.009 269.1 I.5.24 CF₂CF₃ 3.195 297.0 I.5.25

2.919 233.1 I.5.26 CH₂C(CH₃)₂OCH₃ 2.484 233.1 I.5.27 C(CH₃)₃ 3.069 235.1 I.5.28 (−) 3-Cl—C₆H₄ 3.469 289.0 I.5.29 (−) 2-Cl—C₆H₄ 3.116 289.0 I.5.30 (−) 4-C₂H₅O—C₆H₄ 3.358 299.1 I.5.31 (−) 2-CH₃,4-CH₃—C₆H₃ 3.409 283.1 I.5.32 (−) 2-F,5-F—C₆H₃ 3.223 291.0 I.5.33 (−) 4-CH₃O—C₆H₄ 2.990 285.1 I.5.34 CF₃ 0.938 247  

TABLE 12 (I.6)

m/z = cpd.-no R² X R.T. (min) [M + H]+ I.6.1 CH₂C(CH₃)₂OCH₃ OCH₃ 2.041 270.1 I.6.2 C₆H₅ OCH₃ 3.140 247.1 I.6.3

OCH₃ 3.624 247.1 I.6.4 CH₂C₆H₅ OCH₃ 3.617 283.1 I.6.5

OCH₃ 3.860 261.1 I.6.6

OCH₃ 4.114 275.1 I.6.7

OCH₃ 3.585 247.1 I.6.8 (CH₂)₄CH₃ OCH₃ 4.044 263.1 I.6.9 CH₂CH(CH₃)₂ OCH₃ 3.664 249.1 I.6.10

OCH₃ 3.712 247.1 I.6.11 C(CH₃)₃ OCH₃ 3.770 249.1 I.6.12 CH₃ OCH₃ 2.643 207.1 I.6.13

OCH₃ 3.216 287.1 I.6.14 CH₃ OCH(CH₃)CONH₂ 2.082 264.1 I.6.15 CH₃

2.855 300.1 I.6.16 CH(CH₃)₂ OCH₃ 3.427 235.1

TABLE 13 compounds labeled “(−)” are not part of the present invention (I.7)

cpd.-no R² R³ X R.T. (min) m/z = [M + H]+ I.7.1 (−) 3,4-CH₃O—C₆H₃ CH(CH₃)₂ OH 3.193 343.1 I.7.2

CH(CH₃)₂ OCH₃ 4.481 337.0 I.7.3 (−) 4-CH₃O—C₆H₄ CH(CH₃)₂ OH 3.450 313.1 I.7.4 (−) 4-F—C₆H₄ CH(CH₃)₂ OH 3.561 301.1 I.7.5 (−) 2-CH₃O,5-CH₃O—C₆H₃ CH(CH₃)₂ OH 3.379 343.1 I.7.6 (−) 2-CH₃O,4-CH₃O—C₆H₃ CH(CH₃)₂ OH 3.422 343.1 I.7.7 (−) 2-CH₃O—C₆H₄ CH(CH₃)₂ OH 3.390 313.1 I.7.8

CH(CH₃)₂ OH 3.360 247.0 I.7.9 (−) 4-Cl—C₆H₄ CH(CH₃)₂ OH 3.886 275.0 I.7.10 CH₃ CH(CH₃)₂ OH 2.459 221.1 I.7.11

CH(CH₃)₂ OH 1.969 284.1 I.7.12

OH 2.936 271.1 I.7.13 CH₃

OH 2.323 219.1 I.7.14 (−) C₆H₅

OH 3.371 281.1 I.7.15 (−) 2-F—C₆H₄

OH 3.374 299.1 I.7.16 (−) 4-F—C₆H₄

OH 3.480 299.1 I.7.17 CH₂CH₃

OH 2.710 233.1 I.7.18 (−) 3-Cl,4-Cl—C₆H₃ C₆H₅ OH 4.190 385.0 I.7.19 (−) 3-NO₂—C₆H₄ C₆H₅ OH 4.122 376.1 I.7.20 (−) 4-CH₃—C₆H₄ C₆H₅ OH 3.750 331.1 I.7.21 (−) 3-CHF₂O—C₆H₄ C₆H₅ OH 3.679 383.1 I.7.22 (−) 2-F—C₆H₄ C₆H₅ OH 3.513 335.1 I.7.23 (−) 4-CHF₂O—C₆H₄ C₆H₅ OH 3.681 383.1 I.7.24 (−) C₆H₅ C₆H₅ OH 3.520 317.0 I.7.25 (−)

C₆H₅ OH 3.455 361.1 I.7.26 (−) 2-Cl,4-Cl—C₆H₃ C₆H₅ OH 3.927 385.0 I.7.27 CH(CH₃)₃ C₆H₅ OH 3.240 283.1 I.7.28

C₆H₅ OH 2.818 335.1 I.7.29

C₆H₅ OH 2.107 318.1 I.7.30

C₆H₅ OH 3.114 307.1 I.7.31 CH₃ C₆H₅ OH 2.585 255.1 I.7.32 (−) C₆H₅

OH 3.295 307.0 I.7.33 (−) 4-CH₃O—C₆H₄

OCH₃ 3.916 351.1 I.7.34 (−) 4-F—C₆H₄

OH 3.398 325.0 I.7.35 (−) 2-CH₃O—C₆H₄

OH 3.249 337.1 I.7.36 (−) 2-CH₃O,4-CH₃O—C₆H₃

OH 3.312 367.1 I.7.37

OH 2.904 297.6 I.7.38 CH₃

OH 2.298 245.0 I.7.39 CH₃ (CH₂)₂CH₃ OH 2.514 221.1 I.7.40

(CH₂)₂CH₃ OH 3.119 231.0 I.7.41 CH₃ CH₂C(CH₃)₃ OH 2.933 249.1 I.7.42 C₆H₅ 2-F—C₆H₄ OH 3.606 335.1 I.7.43 C₆H₅ 4-F—C₆H₄ OH 3.605 335.1 I.7.44 C₂H₅

OH 2.465 301.1 I.7.45 CH₃

OH 2.147 287.1 I.7.46 (−) CH₃

OCH₃ 3.270 313.1 I.7.47 CH(CH₃)₂ 3-CH₃O—C₆H₄ OH 3.312 313.1 I.7.48 CH₃ 3-CH₃O—C₆H₄ OH 2.699 285.1 I.7.49 CH₃ 4-CH₃O—C₆H₄ OH 2.700 285.1 I.7.50 CH₃

OH 2.297 287.1 I.7.51

CH₃ OH 0.998 237   I.7.52

OH 1.097 263   I.7.53

OCH₃ 1.290 277   I.7.54

OCH₃ 1.283 295   I.7.55

OH 1.069 281   I.7.56

C₆H₅ OH 1.119 317   I.7.57

4-OCH₃—C₆H₄ OH 1.128 347   I.7.58

CH₃ OH 0.985 256   I.7.59

4-CF₃—C₆H₄ OH 1.281 367   I.7.60

4-Br—C₆H₄ OH 1.251 378   I.7.61

4-OCH₃—C₆H₄ OH 1.165 329   I.7.62

C₆H₅ OH 1.155 299   I.7.63

(CH₂)₂CH₃ OH 1.158 265   I.7.64

C(CH₃)₃ OH 1.180 279   I.7.65

4-OCHF₂—C₆H₄ OH 1.222 365   I.7.66

(CH₂)₃CH₃ OH 1.228 279   I.7.67

CH(CH₃)₂ OH 1.155 265   I.7.68

CH₂CH(CH₃)₂ OH 1.218 279   I.7.69

CH₂C(CH₃)₃ OH 1.263 293   I.7.70

(CH₂)₂C₆H₅ OH 1.283 327   I.7.71

OH 1.300 305   I.7.72

OH 1.243 291   I.7.73

CH(CH₃)(CH₂)₂CH₃ OH 1.284 293   I.7.74

SCH₃ 1.401 293   I.7.75

OH 1.198 277   I.7.76

CH₂C₆H₅ OH 1.226 313   I.7.77

(CH₂)₂CH(CH₃)₂ OH 1.295 293   I.7.78

4-OCH₂CH₃—C₆H₄ OH 1.234 343   I.7.79

OH 1.185 277   I.7.80

C(CH₃)₂CH₂CH₃ OH 1.239 293   I.7.81

3-F,4-Br—C₆H₃ OH 1.300 396   I.7.82

OH 1.198 277   I.7.83

3-F,4-F—C₆H₃ OH 1.230 335   I.7.84

OCH(CH₃)₂ NH₂ 1.103 280   I.7.85

OCH(CH₃)₂ OH 1.152 281   I.7.86

OCH(CH₃)₂ SCH₃ 1.431 311   I.7.87

OCH(CH₃)₂ SCH₂C₆H₅ 1.573 387   I.7.88

OCH(CH₃)₂ SC(CH₃)₃ 1.593 353   I.7.89

OCH(CH₃)₂ OCH₂OCH₃ 1.160 281 [M − CH₂OCH₃ + H]+ I.7.90

CH₂CH₃ OH 3.002 251  

TABLE 14 m/z = cpd.-no R.T. (min) [M + H]+ I.8.1

2.119 219.1 1.8.2

3.12 324.1 1.8.3

2.93 261.0 1.8.4

3.60 259.1 1.8.5

3.37 323.0 1.8.6

3.44 257.1

USE EXAMPLES

The herbicidal activity of the isoxazolo[5,4-b]pyridines of formula I was demonstrated by the following greenhouse experiments:

The culture containers used were plastic flowerpots containing loamy sand with approximately 3.0% of humus as the substrate. The seeds of the test plants were sown separately for each species.

For the pre-emergence treatment, the active ingredients, which had been suspended or emulsified in water, were applied directly after sowing by means of finely distributing nozzles. The containers were irrigated gently to promote germination and growth and subsequently covered with transparent plastic hoods until the plants had rooted. This cover caused uniform germination of the test plants, unless this has been impaired by the active ingredients.

For the post-emergence treatment, the test plants were first grown to a height of 3 to 15 cm, depending on the plant habit, and only then treated with the active ingredients which had been suspended or emulsified in water. For this purpose, the test plants were either sown directly and grown in the same containers, or they were first grown separately as seedlings and transplanted into the test containers a few days prior to treatment.

Depending on the species, the plants were kept at 10-25° C. or 20-35° C. The test period extended over 2 to 4 weeks. During this time, the plants were tended, and their response to the individual treatments was evaluated.

Evaluation was carried out using a scale from 0 to 100. 100 means no emergence of the plants, or complete destruction of at least the aerial moieties, and 0 means no damage, or normal course of growth. A good herbicidal activity is given at values of at least 80 and a very good herbicidal activity is given at values of at least 90.

The plants used in the greenhouse experiments belonged to the following species:

Bayer Code Scientific name Common name ABUTH Abutilon theophrasti velvetleaf AGSST Agrostis stolonifera L. white bent ALOMY Alopecurus myosuroides blackgrass AMARE Amaranthus retroflexus L. pigweed AVEFA Avena fatua wild-oat CHEAL Chenopodium album fat-hen LOLMU Lolium multiflorum italian ryegrass MATIN Matricaria inodora horse daisy SETFA Setaria faberi giant foxtail POLCO Polygonum convolvulus wild buckwheat

TABLE 15 Post-emergence treatment of Abutilon theophrasti (velvetleaf) cpd. no. application rate [kg/ha] damage [%] I.5.4 3.0 85 I.2.1 2.0 95 I.1.6 3.0 100 I.1.35 3.0 90 I.2.2 2.0 100 I.2.3 3.0 100 I.2.5 3.0 100 I.2.6 3.0 100 I.7.31 3.0 98 I.2.7 3.0 100 I.2.8 3.0 100 I.7.17 3.0 100 I.1.61 3.0 100 I.1.62 2.0 100 I.8.2 3.0 100 I.1.66 3.0 100 I.1.67 3.0 100 I.1.68 3.0 100 I.1.69 3.0 100 I.1.70 3.0 100 I.1.75 3.0 100 I.8.1 3.0 100 I.7.41 3.0 100 I.7.38 3.0 100 I.7.13 3.0 100 I.7.10 3.0 100 I.7.39 3.0 100 I.2.10 3.0 90 I.4.5 3.0 85 I.2.11 3.0 100 I.4.4 3.0 100 I.2.12 3.0 100 I.2.13 2.0 100 I.2.14 3.0 100 I.2.15 3.0 85 I.2.19 3.0 100 I.2.16 3.0 85 I.2.17 3.0 100 I.2.18 3.0 100 I.2.20 3.0 100 I.2.21 3.0 100 I.2.22 3.0 100 I.2.24 3.0 100 I.2.26 3.0 100 I.2.27 3.0 100 I.4.25 3.0 100 I.4.27 3.0 100 I.2.30 3.0 100 I.2.31 3.0 100 I.2.37 3.0 90 I.2.38 3.0 100 I.2.39 3.0 100 I.2.40 3.0 100 I.2.41 3.0 100 I.2.42 3.0 100 I.2.43 3.0 100 I.2.44 3.0 100

TABLE 16 Post-emergence treatment of Agrostis stolonifera L. (white bent) cpd. no. application rate [kg/ha] damage [%] I.8.6 2.0 80 I.1.10 2.0 90 I.1.31 2.0 85 I.1.39 2.0 90 I.1.49 2.0 85

TABLE 17 Post-emergence treatment of Alopecurus myosuroides (blackgrass) cpd. no. application rate [kg/ha] damage [%] I.1.43 1.0 80

TABLE 18 Post-emergence treatment of Amaranthus retroflexus L. (pigweed) cpd. no. aplication rate [kg/ha] damage [%] I.8.4 1.0 100 I.1.64 0.5 100 I.1.65 1.0 100 I.7.53 1.0 100 I.2.45 1.0 98 I.1.79 1.0 98 I.1.80 1.0 98 I.1.81 1.0 98 I.1.82 1.0 98 I.2.46 1.0 98 I.1.83 1.0 100 I.2.50 1.0 100 I.2.51 1.0 100 I.2.52 1.0 100 I.2.53 1.0 100 I.2.54 1.0 100 I.2.55 1.0 100 I.2.56 1.0 100 I.2.57 1.0 100 I.2.58 1.0 100 I.4.45 1.0 100 I.4.47 1.0 95 I.7.55 1.0 100 I.7.56 1.0 80 I.7.57 1.0 80 I.2.61 1.0 100 I.2.62 1.0 100 I.2.63 1.0 100 I.4.59 1.0 95 I.4.60 0.927 100 I.2.64 1.0 100 I.2.65 1.0 100 I.7.59 1.0 100 I.7.60 1.0 100 I.7.61 1.0 100 I.7.62 1.0 100 I.2.66 1.0 100 I.7.63 1.0 100 I.7.64 1.0 100 I.7.65 1.0 100 I.7.90 1.0 100 I.2.71 1.0 100 I.4.63 1.0 100 I.7.68 1.0 100 I.7.69 1.0 100

TABLE 19 Post-emergence treatment of Avena fatua (spring-wild oat) cpd. no. application rate [kg/ha] damage [%] I.1.35 3.0 85 I.1.39 2.0 85 I.1.43 1.0 90 I.1.61 3.0 100 I.1.63 3.0 80 I.8.2 3.0 90 I.1.66 3.0 80 I.1.67 3.0 95

TABLE 20 Post-emergence treatment of Chenopodium album (fat-hen) cpd. no. application rate [kg/ha] damage [%] I.1.21 1.0 100 I.8.4 1.0 100 I.1.65 1.0 100 I.7.53 1.0 90 I.2.45 1.0 98 I.1.79 1.0 85 I.1.80 1.0 98 I.1.81 1.0 98 I.1.82 1.0 98 I.2.46 1.0 98 I.1.83 1.0 100 I.2.50 1.0 100 I.2.51 1.0 100 I.2.52 1.0 98 I.2.53 1.0 100 I.2.54 1.0 100 I.2.55 1.0 100 I.2.56 1.0 100 I.2.57 1.0 100 I.2.58 1.0 100 I.7.55 1.0 100 I.7.56 1.0 90 I.7.57 1.0 98 I.7.58 1.0 95 I.2.59 1.0 95 I.2.61 1.0 100 I.2.62 1.0 100 I.2.63 1.0 100 I.4.59 1.0 100 I.4.60 0.927 100 I.7.61 1.0 100 I.7.62 1.0 100 I.2.66 1.0 100 I.7.63 1.0 100 I.7.64 1.0 100 I.7.65 1.0 100 I.7.90 1.0 100 I.7.66 1.0 100 I.7.67 1.0 100 I.2.69 1.0 95 I.2.71 1.0 100 I.4.63 1.0 100 I.7.68 1.0 100

TABLE 21 Post-emergence treatment of Lolium multiflorum (italian ryegrass) cpd. no. application rate [kg/ha] damage [%] I.1.21 1.0 100

TABLE 22 Post-emergence treatment of Matricaria inodora (horse daisy) cpd. no. application rate [kg/ha] damage [%] I.7.34 2.0 85 I.1.2 2.0 90 I.1.10 2.0 85 I.1.24 2.0 100 I.1.31 2.0 95 I.1.49 2.0 98 I.2.4 2.0 98

TABLE 23 Post-emergence treatment of Setaria faberi (giant foxtail) cpd. no. application rate [kg/ha] damage [%] I.7.32 3.0 80 I.8.6  2.0 80 I.2.1  2.0 100 I.7.4  3.0 80 I.7.7  3.0 85 I.8.5  3.0 80 I.5.8  3.0 85 I.1.6  3.0 95 I.2.2  2.0 90 I.2.3  3.0 85 I.2.5  3.0 80 I.2.6  3.0 95 I.8.3  3.0 85 I.2.7  3.0 100 I.5.13 3.0 95 I.2.8  3.0 80 I.7.17 3.0 90 I.7.9  3.0 85 I.4.2  3.0 85 I.4.6  3.0 80 I.2.10 3.0 85 I.2.11 3.0 100 I.2.12 3.0 90 I.4.3  3.0 90 I.2.13 2.0 95 I.2.14 3.0 90 I.2.15 3.0 100 I.2.19 3.0 85 I.2.16 3.0 100 I.2.20 3.0 95 I.4.19 3.0 100 I.2.25 3.0 95 I.7.51 3.0 90

3.0 98

TABLE 24 Post-emergence treatment of Polygonum convolvulus (wild buckwheat) cpd. no. application rate [kg/ha] damage [%] I.7.58 1.0 90 I.2.59 1.0 90 I.2.64 1.0 80 I.2.65 1.0 100 I.7.59 1.0 100 I.7.60 1.0 100 I.7.66 1.0 100 I.7.67 1.0 100 I.2.69 1.0 85 I.7.69 1.0 100 

The invention claimed is:
 1. A compound of formula (I)

wherein R¹ is hydrogen, halogen, C₁-C₆-alkyl, or C₁-C₆-haloalkyl; R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl, or C₂-C₆-alkynyl; R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl, C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl, C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy, C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino, N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, or phenyl; wherein heterocyclyl is a 5- or 6-membered saturated, partially unsaturated or aromatic monocyclic ring, which contains 1, 2, 3, or 4 heteroatoms selected from the group consisting of O, N and S as ring members; and wherein the heterocyclyl and phenyl moieties of R³ can be unsubstituted or substituted with one or more radicals selected from the group consisting of halogen, hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, and phenyl; X is OR⁴; R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, or C₂-C₆-alkynyl; or its agriculturally useful salt with the exception of isoxazolo[5,4-b]pyridine compounds of formula I, wherein R¹ is hydrogen, R² is cyclopropyl, R³ is CH₃, X is OR⁴ and R⁴ is hydrogen, C₁-C₆-alkyl, cyanomethyl, or 2-Cl-2-propen-1-yl; R¹ is hydrogen, R² is cyclopropyl, R³ is CH₂C(CH₃)₃, (CH₂)₂CH₃, CH(CH₃)₂, C(CH₃)₃, cyclopropyl, phenyl, 2-F-phenyl, 4-F-phenyl, 4-methylphenyl, 4-methoxyphenyl, 2-furan-yl, 1,3,5-trimethyl-1H-pyrazol-4-yl, 1-ethyl-5-methyl-1H-pyrazol-4-yl, X is OR⁴ and R⁴ is hydrogen, methyl or ethyl; R¹ is hydrogen, R² is methyl, R³ is CH₃, CH₂C(CH₃)₃, (CH₂)₂CH₃, CH(CH₃)₂, C(CH₃)₃, cyclopropyl, phenyl, 4-methylphenyl, 4-methoxyphenyl, 3-methoxyphenyl, 4-fluorophenyl, 3,4-dichlorophenyl, 2-furan-yl, 1,3,5-trimethyl-1H-pyrazol-4-yl, 1-ethyl-5-methyl-1H-pyrazol-4-yl, X is OR⁴ and R⁴ is hydrogen, methyl or ethyl; R¹ is hydrogen, R² is ethyl, R³ is CH₃, (CH₂)₂CH₃, CH(CH₃)₂, CH₂C(CH₃)₃, cyclopropyl, 1,3,5-trimethyl-1H-pyrazol-4-yl, X is OR⁴ and R⁴ is hydrogen, methyl or ethyl; R¹ is hydrogen, R² is i-propyl, R³ is CH₃, CH₂C(CH₃)₃, (CH₂)₂CH₃, CH(CH₃)₂, C(CH₃)₃, cyclopropyl, phenyl, 3-methoxyphenyl, 2-furan-yl; X is OR⁴ and R⁴ is hydrogen, methyl or ethyl; and R¹ is chlorine, R² is methyl, cyclopropyl, R³ is methyl, X is OR⁴ and R⁴ is hydrogen or methyl.
 2. A compound of formula (I)

wherein R¹ is hydrogen; R² is cyclopropyl; R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl, C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkenyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy, C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino, N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, or phenyl; wherein heterocyclyl is a 5- or 6-membered saturated, partially unsaturated or aromatic monocyclic ring, which contains 1, 2, 3, or 4 heteroatoms selected from the group consisting of O, N and S as ring members; and wherein the heterocyclyl and phenyl moieties of R³ can be unsubstituted or substituted with one or more radicals selected from the group consisting of halogen, hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, C₁-C₄-alkylthio, C₁-C₄-allkylsulfinyl, C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, and phenyl; X is OR⁴; R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl, C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-alkoxy-C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₂-C₆-alkenyloxy-C₁-C₆-alkyl, C₂-C₆-haloalkenyloxy-C₁-C₆-alkyl, C₁-C₆-alkoxycarbonyl-C₁-C₆-alkyl, aminocarbonyl-C₁-C₆-alkyl, C₁-C₆-alkyl-aminocarbonyl-C₁-C₆-alkyl, N,N-di-(C₁-C₆-alkyl)-aminocarbonyl-C₁-C₆-alkyl, [N—(C₃-C₆-cycloalkyl-C₁-C₆-alkyl), N—(C₁-C₆-alkyl)]-aminocarbonyl-C₁-C₆-alkyl, C₁-C₆-alkoxy-aminocarbonyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl-C₂-C₆-alkenyl, C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, heterocyclyl, phenyl, heterocyclylcarbonyl, phenylcarbonyl, phenylcarbonyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl, or phenyl-C₁-C₆-alkyl; wherein heterocyclyl is a 5- or 6-membered saturated, partially unsaturated or aromatic monocyclic ring, which contains 1, 2, 3, or 4 heteroatoms selected from the group consisting of O, N and S as ring members; and wherein the phenyl and heterocyclyl moieties of R⁴ can be unsubstituted or substituted with one or more radicals selected from the group consisting of halogen, C₁-C₄-alkyl, C₁-C₄-haloalkyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, heterocyclyl, and phenyl; or its agriculturally useful salt; with the exception of: Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2-fluorophenyl)-methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-[4-(methoxycarbonyl)-3,5-dimethyl-1H-pyrrol-2-yl]-1-methyl-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(2-methoxy-4-methylphenyl)-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-[5-(2-furanyl)-3-isoxazolyl]methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-1-(5-phenyl-1,3,4-oxadiazol-2-yl)ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-chloro-2-propen-1-yl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(3,4-dimethoxyphenyl)-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1-ethyl-5-methyl-1H-pyrazol-4-yl)-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(4-methoxyphenyl)-1-methyl-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-[2-(3-thienyl)-4-thiazolyl]methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(4-fluorophenyl)-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-pyridinylmethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(3-fluoro-4-methoxyphenyl)-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(4-fluorophenyl)-1-methyl-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-oxo-2-(pentylamino)ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-(5-bromo-2-methoxyphenyl)methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-1-methyl-2-oxo-2-phenylethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-1-methyl-2-[(1-methylethyl)amino]-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(4-methoxyphenyl)-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-(6-chloro-3-pyridinyl)methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-amino-1-methyl-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-(2-chloro-6-fluorophenyl)methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(2-bromophenyl)-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(1,1-dimethylethoxy)-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-[2,5-dimethyl-1-(3-methylbutyl)-1H-pyrrol-3-yl]-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-[2-(difluoromethoxy)-5-methylphenyl]-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(2-methoxyphenyl)-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-oxo-2-(2,3,4,5-tetramethylphenyl)ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-[5-(2-thienyl)-1,3,4-oxadiazol-2-yl]methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(4-methylphenyl)-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-(3-fluoro-4-methoxyphenyl)methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(4-methoxyphenyl)ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-(1-butyl-1H-tetrazol-5-yl)methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-1-methylethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-[(1-methylbutyl)amino]-2-oxoethyl ester;

Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-cyanomethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-[3-(methoxycarbonyl)-2-furanyl]methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-(3-methyl-5-isoxazolyl)methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-(5-chloro-1,2,3-thiadiazol-4-yl)methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1,1-dimethylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-phenyl-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(4-methoxyphenyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-methoxy-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-(2,4-dimethoxyphenyl)-2-oxoethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl-, ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-(3,5-dimethyl-4-isoxazolyl)methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-[3-(2-thienyl)-1,2,4-oxadiazol-5-yl]methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl)-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2,3-dichlorophenyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-(2-ethyl-4-thiazolyl)methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2,2-dimethylpropyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2,2-dimethylpropyl) methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2,2-dimethylpropyl) ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-propyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-propyl methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-propyl ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2-furanyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2-furanyl) methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2-furanyl) ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-phenyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-phenyl ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1-methylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1-methylethyl) methyl ester; and Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1-methylethyl) ethyl ester.
 3. The compound of claim 2, wherein R¹ is hydrogen; R² is cyclopropyl; R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl, C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl, C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy, C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino, N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, or phenyl; wherein heterocyclyl is a 5- or 6-membered saturated, partially unsaturated or aromatic monocyclic ring, which contains 1, 2, 3, or 4 heteroatoms selected from the group consisting of O, N and S as ring members; and wherein the heterocyclyl and phenyl moieties of R³ can be unsubstituted or substituted with one or more radicals selected from the group consisting of halogen, hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkoxy, C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, and phenyl; X is OR⁴; R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, or C₂-C₆-alkynyl; or its agriculturally useful salt; with the exception of: Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2-fluorophenyl)-methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-2-chloro-2-propen-1-yl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1-ethyl-5-methyl-1H-pyrazol-4-yl)-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(4-fluorophenyl) methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(4-methoxyphenyl) methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(4-methylphenyl) methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-1-methylethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl-cyanomethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1,1-dimethylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-phenyl methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(4-methoxyphenyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl)-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2,2-dimethylpropyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2,2-dimethylpropyl) methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2,2-dimethylpropyl) ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-propyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-propyl methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-propyl ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2-furanyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2-furanyl) methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2-furanyl) ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-phenyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-phenyl ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl ethyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1-methylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1-methylethyl) methyl ester; and Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1-methylethyl) ethyl ester.
 4. The compound of claim 1, wherein R¹ is hydrogen, halogen, C₁-C₆-alkyl, or C₁-C₆-haloalkyl; R² is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₂-C₆-alkenyl, or C₂-C₆-alkynyl; R³ is hydrogen, halogen, hydroxy, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-hydroxyalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₃-C₆-cycloalkyl-C₁-C₆-alkyl, C₃-C₆-halocycloalkyl-C₁-C₆-alkyl, C₃-C₆-cycloalkyl, C₃-C₆-halocycloalkyl, C₁-C₄-alkyl-C₃-C₆-cycloalkyl, C₃-C₆-cycloalkenyl, C₃-C₆-halocycloalkenyl, phenyl-C₁-C₆-alkyl, heterocyclyl-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl, C₂-C₆-haloalkynyl, C₁-C₆-alkoxy, C₁-C₆-haloalkoxy, C₁-C₆-alkylthio, C₁-C₆-haloalkylthio, amino, C₁-C₆-alkylamino, N,N-di-(C₁-C₆)-alkylamino, heterocyclyl, or phenyl; wherein heterocyclyl is a 5- or 6-membered saturated, partially unsaturated or aromatic monocyclic ring, which contains 1, 2, 3, or 4 heteroatoms selected from the group consisting of O, N and S as ring members; and wherein the heterocyclyl and phenyl moieties of R³ can be unsubstituted or substituted with one or more radicals selected from the group consisting of halogen, hydroxy, nitro, cyano, C₁-C₄-alkyl, C₁-C₄-haloalkoxy, C₁-C₄-alkoxy-C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₂-C₆-alkenyl, C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, C₁-C₄-alkoxycarbonyl, C₁-C₄-alkylthio, C₁-C₄-alkylsulfinyl, C₁-C₄-alkylsulfonyl, amino, C₁-C₄-alkylamino, N,N-di-(C₁-C₄)-alkylamino, heterocyclyl, and phenyl; X is OR⁴; R⁴ is hydrogen; or its agriculturally useful salt; with the exception of: Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1,1-dimethylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(4-methoxyphenyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2,2-dimethylpropyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-propyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(2-furanyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-phenyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-methyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-cyclopropyl-3-(1-methylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dimethyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-propyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(1-methylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(1,1-dimethylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(2,2-dimethylpropyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-cyclopropyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-phenyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(4-methylphenyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(3-methoxyphenyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(4-methoxyphenyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(4-fluorophenyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(3,4-dichlorophenyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(2-furanyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-methyl-3-(1-ethyl-5-methyl-1H-pyrazol-4-yl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-methyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-propyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-(1-methylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-(2,2-dimethylpropyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-cyclopropyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-ethyl-3-(1,3,5-trimethyl-1H-pyrazol-4-yl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-(1-methylethyl)-3-methyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-(1-methylethyl)-3-propyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-bis(1-methylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-(1-methylethyl)-3-(1,1-dimethylethyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-(1-methylethyl)-3-(2,2-dimethylpropyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-(1-methylethyl)-3-cyclopropyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-(1-methylethyl)-3-phenyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-(1-methylethyl)-3-(3-methoxyphenyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 6-(1-methylethyl)-3-(2-furanyl); Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 5-chloro-6-cyclopropyl-3-methyl; and Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 5-chloro-3,5-dimethyl.
 5. A composition comprising a herbicidally active amount of the compound of claim 1 and auxiliaries customary for formulating crop protection agents.
 6. A composition comprising a herbicidally active amount of the compound of claim 2 and auxiliaries customary for formulating crop protection agents.
 7. A composition comprising a herbicidally active amount of the compound of claim 3 and auxiliaries customary for formulating crop protection agents.
 8. A composition comprising a herbicidally active amount of the compound of claim 4 and auxiliaries customary for formulating crop protection agents.
 9. A method for preparing the composition according to claim 5, which comprises mixing a herbicidally active amount of the compound and auxiliaries customary for formulating crop protection agents.
 10. A method for preparing the composition according to claim 6, which comprises mixing a herbicidally active amount of the compound and auxiliaries customary for formulating crop protection agents.
 11. A method for preparing the composition according to claim 7, which comprises mixing a herbicidally active amount of the compound and auxiliaries customary for formulating crop protection agents.
 12. A method for preparing the composition according to claim 8, which comprises mixing a herbicidally active amount of the compound and auxiliaries customary for formulating crop protection agents.
 13. A compound of formula I according to claim 1, wherein X is OR⁴; R¹ is hydrogen; R² is cyclopropyl; R³ is cyclopropyl, 1-methyl-ethyl or 4-difluoromethoxy-phenyl; R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₁-C₆-cyanoalkyl, C₁-C₆-alkoxy-C₁-C₆-alkyl, C₁-C₆-haloalkoxy-C₁-C₆-alkyl, C₂-C₆-alkenyl, C₂-C₆-haloalkenyl, C₂-C₆-alkynyl; or an agriculturally useful salt; with the exception of: Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl-, methyl ester; Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl-, ethyl ester.
 14. A compound of formula I according to claim 13, wherein R³ is cyclopropyl; R⁴ is hydrogen; and their agriculturally useful salts; with the exception of: Isoxazolo[5,4-b]pyridine-4-carboxylic acid, 3,6-dicyclopropyl.
 15. An agriculturally useful salt of the compounds of formula I according to claim 1, wherein the agriculturally useful salt comprises an ammonium cation, wherein one to four hydrogen atoms may be replaced by C₁-C₄-alkyl, hydroxy-C₁-C₄-alkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl, hydroxy-C₁-C₄-alkoxy-C₁-C₄-alkyl, phenyl or benzyl.
 16. An agriculturally useful salt of the compounds of formula I according to claim 1, wherein the agriculturally useful salt comprises a cation selected from ammonium, dimethylammonium, diisopropylammonium, tetramethylammonium, tetrabutylammonium, 2-(2-hydroxyeth-1-oxy)eth-1-ylammonium, di(2-hydroxyeth-1-yl)ammonium and trimethylbenzylammonium.
 17. An agriculturally useful salt of the compounds of formula I according to claim 1, wherein the agriculturally useful salt comprises an ammonium cation. 